Methods and compositions for concrete production

ABSTRACT

The invention provides compositions and methods directed to carbonation of a cement mix during mixing. The carbonation may be controlled by one or more feedback mechanisms to adjust carbon dioxide delivery based on one or more characteristics of the mix or other aspects of the mixing operation.

CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.14/701,456, filed Apr. 30, 2015, which is a continuation of PCTApplication No. PCT/CA2014/050611, filed Jun. 25, 2014, which claimspriority to U.S. Provisional Patent Application Ser. No. 61/980,505,filed Apr. 16, 2014 and is a continuation-in-part of U.S. patentapplication Ser. No. 14/249,308 (now U.S. Pat. No. 9,108,883), filedApr. 9, 2014. Moreover, both PCT Application No. PCT/CA2014/050611 andU.S. patent application Ser. No. 14/249,308, claim priority to U.S.Provisional Patent Application Ser. No. 61/839,312, filed Jun. 25, 2013,U.S. Provisional Patent Application Ser. No. 61/847,254, filed Jul. 17,2013, U.S. Provisional Patent Application Ser. No. 61/879,049, filedSep. 17, 2013, U.S. Provisional Patent Application Ser. No. 61/925,100,filed Jan. 8, 2014, and U.S. Provisional Patent Application Ser. No.61/938,063, filed Feb. 10, 2014. Each of the abovementioned applicationsis entirely incorporated herein by reference.

BACKGROUND OF THE INVENTION

Cement mixes, such as concrete mixes, are used in a multitude ofcompositions and procedures throughout the world. In addition,greenhouse gases such as carbon dioxide are a growing concern worldwide.There is a need for methods and compositions to contact cement mixeswith carbon dioxide and for cement mixes containing incorporated carbondioxide and carbonation products.

SUMMARY OF THE INVENTION

In one aspect, the invention provides methods. In certain embodiments,the invention provides a method for producing a carbonated cement mix ina mix operation in a cement mix apparatus comprising (i) contacting acement mix comprising cement binder and aggregate in a mixer with carbondioxide while the cement mix is mixing, (ii) monitoring a characteristicof the cement binder, the cement mix, a gas mixture in contact with thecement mix or the mixer, or a component of the cement mix apparatus; and(iii) modulating the exposure of the cement mix to the carbon dioxide oranother characteristic of the cement mix operation, or a combinationthereof according to the characteristic monitored in step (ii). Incertain embodiments, the characteristic monitored in step (ii) comprisesat least one of: (a) mass of cement binder added to the cement mix, (b)location of the cement binder in the mix apparatus, (c) carbon dioxidecontent of a gas mixture within the mixer in contact with the cementmix, (d) carbon dioxide content of a gas mixture exiting from the mixer,(e) carbon dioxide content of gas mixture in the vicinity of the mixapparatus, (f) temperature of the cement mix or a component of the mixapparatus in contact with the cement mix, (g) rheology of the cementmix, (h) moisture content of the cement mix, or (i) pH of the cementmix; for example carbon dioxide content of a gas mixture exiting fromthe mixer, such as wherein the exposure of the cement mix to carbondioxide is modulated when the carbon dioxide content of the gas mixturereaches a threshold value, or when rate of change of the carbon dioxidecontent of the gas mixture reaches a threshold value. In certainembodiments, the exposure of the cement mix to carbon dioxide ismodulated when the temperature of the cement mix or a component of themix apparatus in contact with the cement mix reaches a threshold value.In certain embodiments, a plurality of characteristics is monitored instep (ii), comprising at least two of (a) mass of cement binder added tothe cement mix, (b) location of the cement binder in the mix apparatus,(c) carbon dioxide content of a gas mixture within the mixer in contactwith the cement mix, (d) carbon dioxide content of a gas mixture exitingfrom the mixer, (e) carbon dioxide content of gas mixture in thevicinity of the mix apparatus, (f) temperature of the cement mix or acomponent of the mix apparatus in contact with the cement mix, (g)rheology of the cement mix, (h) moisture content of the cement mix, or(i) pH of the cement mix. In certain embodiments, the additional(another) characteristic of the mix operation comprises (a) whether ornot an admixture is added to the cement mix, (b) type of admixture addedto the cement mix, (c) timing of addition of admixture to the cementmix, (d) amount of admixture added to the cement mix, (e) amount ofwater added to the cement mix, (f) timing of addition of water to thecement mix, (g) cooling of the cement mix during or after carbon dioxideaddition, or a combination thereof. In certain embodiments, thecharacteristic is monitored by one or more sensors which transmitinformation regarding the characteristic to a controller which processesthe information and determines if a modulation of carbon dioxideexposure or another characteristic of the mix operation is required and,if so, transmits a signal to one or more actuators to carry out themodulation of carbon dioxide exposure or other characteristic of the mixoperation. The controller can, e.g., store and process the informationobtained regarding the characteristic monitored in step (ii) for a firstbatch of cement mix and adjust conditions for a subsequent second cementmix batch based on the processing. In certain embodiments, thecontroller, one or more sensors, one or more actuators, or combinationthereof, transmits information regarding the characteristics monitoredand conditions modulated to a central controller that receivesinformation from a plurality of controllers, sensors, actuators, orcombination thereof, from a plurality of separate mix operations. Incertain embodiments, the exposure of the cement mix to the carbondioxide is modulated in such a way as to achieve an efficiency ofcarbonation of at least 60%, wherein efficiency of carbonation is theamount of carbon dioxide retained in the cement mix per the total amountof carbon dioxide to which the cement mix is exposed during mixing.

In another aspect, the invention provides apparatus. In certainembodiments, the invention provides an apparatus for carbonating acement mix comprising a cement binder and aggregate in a cement mixapparatus during a mix operation, comprising (i) a mixer for mixing thecement mix; (ii) a system for contacting the cement mix in the mixerwith carbon dioxide operably connected to the mixer and comprising anactuator for modulating a flow of carbon dioxide to the mixer; (iii) asensor positioned and configured to monitor a characteristic of the mixoperation; and to transmit information regarding the characteristic to acontroller; (iv) the controller, wherein the controller is configured toprocess the information and determine whether or not and/or to whatdegree to modulate the flow of carbon dioxide to the mixer and totransmit a signal to the actuator to modulate the flow of carbon dioxideto the mixer. In certain embodiments, the characteristic of the mixoperation comprises a characteristic of the cement binder, the cementmix, a gas mixture in contact with the cement mix or the mixer, or acomponent of the cement mix apparatus. In certain embodiments, thecharacteristic monitored by the sensor comprises at least one of: (a)mass of cement binder added to the cement mix, (b) location of thecement binder in the mix apparatus, (c) carbon dioxide content of a gasmixture within the mixer in contact with the cement mix, (d) carbondioxide content of a gas mixture exiting from the mixer, (e) carbondioxide content of gas mixture in the vicinity of the mix apparatus, (f)temperature of the cement mix or a component of the mix apparatus incontact with the cement mix, (g) rheology of the cement mix, (h)moisture content of the cement mix, or (i) pH of the cement mix. Incertain embodiments, the characteristic monitored by the sensorcomprises carbon dioxide content of a gas mixture exiting from themixer. In certain embodiments, the characteristic monitored by thesensor comprise the temperature of the cement mix or a component of themix apparatus in contact with the cement mix. In certain embodiments,the apparatus comprises a plurality of sensors configured to monitor atleast two characteristics comprising (i) mass of cement binder added tothe cement mix, (ii) location of the cement binder in the mixer, (iii)carbon dioxide content of a gas mixture within the mixer in contact withthe cement mix, (iv) carbon dioxide content of gas mixture exiting fromthe mixer, (v) carbon dioxide content of gas mixture in the vicinity ofthe mixer, (vi) temperature of the cement mix or a component in contactwith the cement mix, (vii) rheology of the cement mix, (viii) moisturecontent of the cement mix. In certain embodiments the apparatus furthercomprises an actuator configured to modulate an additionalcharacteristic of the mix operation, wherein the actuator is operablyconnected to the controller and wherein the controller is configured tosend a signal to the actuator to modulate the additional characteristicbased on the processing of information from one or more sensors, such asan actuator configured to modulate addition of admixture to the cementmix, type of admixture added to the cement mix, timing of addition ofadmixture to the cement mix, amount of admixture added to the cementmix, amount of water added to the cement mix, timing of addition ofwater to the cement mix, or cooling the cement mix during or aftercarbon dioxide addition. In certain embodiments, the controller isconfigured to store and process the information obtained regarding thecharacteristic monitored by the sensor for a first batch of cement mixand to adjust conditions for a subsequent second cement mix batch basedon the processing to optimize one or more aspects of the mix operation.The controller may be further configured to receive and processinformation regarding one or more characteristics of the cement mixmeasured after the cement mix leaves the mixer, and to transmit signalsto one or more actuators configured to adjust conditions for the secondcement mix batch based on the processing to modulate contact with thecarbon dioxide or another characteristic of the mix operation. Incertain embodiments, the controller, sensor, actuator, or combinationthereof, is configured to transmit information regarding thecharacteristics monitored and conditions modulated to a centralcontroller that is configured to receive information from a plurality ofcontrollers, sensors, actuators, or combination thereof, each of whichtransmits information from a separate mix operation to the centralcontroller. The central controller can be configured to process theinformation received from the plurality of controllers, sensors,actuators, or combination thereof and processes the information tomodulate one or more of the plurality of mix operations. In certainembodiments, the processor is configured to control the actuator suchthat exposure of the cement mix to the carbon dioxide is modulated insuch a way as to achieve an efficiency of carbonation of at least 60%,wherein efficiency of carbonation is the amount of carbon dioxideretained in the cement mix per the total amount of carbon dioxide towhich the cement mix is exposed during mixing.

In certain embodiments, the invention provides a controller forcontrolling a cement mix mixing operation comprising carbonation of thecement mix in a mixer by exposing the cement mix to carbon dioxide,wherein the controller comprises (i) an input port for receiving asignal from a sensor that monitors a characteristic of the cement mixmixing operation; (ii) a processor for processing the signal from thesensor and formulating an output signal to modulate the exposure of thecement mix to carbon dioxide or to modulate a characteristic of thecement mix; and (iii) an output port for transmitting the output signalto an actuator that modulates the exposure of the cement mix to carbondioxide or that modulates a characteristic of the cement mix. In certainembodiments, the input port is configured to receive a plurality ofsignals from a plurality of sensors, and the processor is configured toprocess the plurality of signals and formulate an output signal tomodulate the exposure of the cement mix to carbon dioxide or to modulatea characteristic of the cement mix. In certain embodiments, theprocessor is configured to formulate a plurality of output signals tomodulate the exposure of the cement mix to carbon dioxide or to modulatea characteristic of the cement mix and the output port is configured totransmit the plurality of signals.

In certain embodiments, the invention provides a network comprising (i)a plurality of spatially separate cement mix operations, each of whichcomprises at least one sensor for monitoring at least one characteristicof its operation, operably connected to (ii) a central processing unit,to which each sensor sends its information and which stores and/orprocesses the information. In certain embodiments, the network comprisesat least one mix operation in which the cement mix is carbonated.

Additional aspects and advantages of the present disclosure will becomereadily apparent to those skilled in this art from the followingdetailed description, wherein only illustrative embodiments of thepresent disclosure are shown and described. As will be realized, thepresent disclosure is capable of other and different embodiments, andits several details are capable of modifications in various obviousrespects, all without departing from the disclosure. Accordingly, thedrawings and description are to be regarded as illustrative in nature,and not as restrictive.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 provides a schematic view of a stationary mixer with apparatusfor providing carbon dioxide to a hydraulic cement mix during mixer.

FIG. 2 provides a schematic view of a mobile mixer (ready mix truck)provided with a detachable carbon dioxide delivery system to delivercarbon dioxide to the mixing concrete.

FIG. 3 provides a schematic view of a mobile mixer (ready mix truck)provided with an attached carbon dioxide delivery system to delivercarbon dioxide to the mixing concrete.

FIG. 4 shows 7-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at various doses.

FIG. 5 shows 7-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at various doses and with various watercontents.

FIG. 6 shows 7-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at various doses.

FIG. 7 shows 14-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at various doses.

FIG. 8 shows 28-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at various doses.

FIG. 9 shows 7-, 14-, and 28-day compressive strengths of concreteprepared from wet mixes exposed to carbon dioxide with two differentwater contents.

FIG. 10 shows 7- and 28-day compressive strengths of concrete preparedfrom wet mixes exposed to carbon dioxide at two different doses and twodifferent water contents.

FIG. 11 shows 7-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at two different doses and higher watercontent.

FIG. 12 shows 7-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at two different doses and higher watercontent.

FIG. 13 shows 7-day compressive strengths of concrete prepared from wetmixes exposed to carbon dioxide at two different doses and higher watercontent.

FIG. 14 shows slump of concrete wet mixes exposed to carbon dioxide attwo different doses and five different water contents.

FIG. 15 provides a graphic illustration of slump at various times aftertruck arrival for carbonated concrete batches prepared in a ready mixoperation.

FIG. 16 provides a graphic illustration of compressive strengthdevelopment in carbonated concrete prepared in a ready mix operation,compared to control, uncarbonated concrete, at 3, 7, 28, and 56 days.

FIG. 17 provides a graphic illustration of A) Rapid chloride penetrationtests and B) Flexural strength tests on carbonated concrete prepared ina ready mix operation compared to control, uncarbonated concrete.

FIG. 18 provides a graphic illustration of compressive strengths at 1,7, 28, and 56 days for concretes prepared in a ready mix operation with0, 0.5, or 1.0% bwc carbon dioxide delivered to the concrete.

FIG. 19 provides a graphic illustration of compressive strengths at 1,7, 28, and 56 days for concretes prepared in a ready mix operation with0, 1.0, or 1.5% bwc carbon dioxide delivered to the concrete, and 0.05%sodium gluconate admixture added to the 1.5% batch.

FIG. 20 provides a graphic illustration of cylinder mass for constantvolume cylinders (density), a proxy for compressive strength, in drycast concrete prepared as uncarbonated or carbonated for 1 or 2 minutes,with addition of sodium gluconate admixture at various concentrations.

FIG. 21 provides a graphic illustration of cylinder mass for constantvolume cylinders (density), a proxy for compressive strength, in drycast concrete prepared as uncarbonated or carbonated for 90 s at 50 LPMwith addition of sodium gluconate admixture at 0.24, 0.30, 0.36, or0.42% bwc.

FIG. 22 provides a graphic illustration of cylinder mass for constantvolume cylinders (density), a proxy for compressive strength, in drycast concrete prepared as uncarbonated or carbonated for 90 s at 50 LPMwith addition of sodium gluconate admixture at 0.30 or 0.42% bwc.

FIG. 23 provides a graphic illustration of cylinder mass for constantvolume cylinders (density), a proxy for compressive strength, in drycast concrete prepared as uncarbonated or carbonated for 90 s at 50 LPMwith addition of sodium gluconate admixture at 0.30 or 0.42% bwc. Allsamples included Rainbloc and Procast admixtures, with one 0.30% samplehaving Procast added after carbon dioxide delivery.

FIG. 24 provides a graphic illustration of slump, relative to untreatedcontrol, in carbonated mortar mixes treated with sodium glucoheptonate,fructose, or sodium gluconate at various concentrations.

FIG. 25 provides a graphic illustration of effects on slump of fructoseor sodium gluconate added to a mortar mix pre-, mid-, orpost-carbonation.

FIG. 26 provides a graphic illustration of effects on 24-hourcompressive strength, compared to uncarbonated control, of a carbonatedmortar preparation in which sodium gluconate was added either before orafter carbonation at doses of 0, 0.025, 0.05, and 0.75%.

FIG. 27 provides a graphic illustration of the effects of temperature ofmaterials on rate of carbon dioxide uptake in a mortar mix. Temperatureswere 7° C., 15° C. and 25° C.

FIG. 28 provides a graphic illustration of the effects of heated or coldgases, or dry ice, on carbon dioxide uptake in a cement paste system.

FIG. 29 provides a graphic illustration of the effects of plasticizersand calcium hydroxide on 24 hour compressive strength in carbonated anduncarbonated mortar mixes.

FIG. 30 provides a graphic illustration of the effects of CaO, NaOH,Ca(NO₂)₂, and CaCl₂ on 24 hour compressive strength in carbonated anduncarbonated mortar mix.

FIG. 31 provides a graphic illustration of the effect of carbon dioxideaddition before or after the addition of an air entrainer on mortardensity.

FIGS. 32a and 32b provides a table showing the results of tests forcarbon dioxide uptake, compressive strength, water absorption, anddensity for blocks produced in a precast dry cast operation withcarbonation at the mixer, feedbox, or both, in a standard block mix.

FIG. 33 is a graphic illustration of the effects of sodium gluconatedose on 7-, 28- and 56-day compressive strengths of carbonated blocksproduced in a dry cast operation, with various doses of sodiumgluconate, compared to uncarbonated control.

FIGS. 34a and 34b provides a table showing the results of tests forcarbon dioxide uptake, compressive strength, water absorption, anddensity for blocks produced in a precast dry cast operation withcarbonation at the mixer in a limestone block mix.

FIGS. 35a and 35b provides a table showing the results of tests forcarbon dioxide uptake, compressive strength, water absorption, anddensity for blocks produced in a precast dry cast operation withcarbonation at the mixer in a lightweight block mix.

FIG. 36 provides a graphic illustration of 7-, 28-, and 56-daycompressive strengths of lightweight blocks produced in a dry castoperation with carbonation and various doses of sodium gluconate.

FIGS. 37a and 37b provide a table showing the results of tests forcarbon dioxide uptake, compressive strength, water absorption, anddensity for blocks produced in a precast dry cast operation withcarbonation at the mixer in a sandstone block mix.

FIG. 38 provides a graphic illustration of 7-, 28-, and 56-daycompressive strengths of sandstone blocks produced in a dry castoperation with carbonation and various doses of sodium gluconate.

FIG. 39 provides a graphic illustration of the relationship betweenoptimum dose of sodium gluconate and cement content in carbonated drycast blocks.

FIG. 40 provides a graphic illustration of compressive strength anddensity of carbonated and uncarbonated precast medium weight blocks,with or without treatment with 0.25% sodium gluconate.

FIG. 41 provides a table of results of third party testing of mediumweight blocks produced in a precast operation as uncarbonated,carbonated, and carbonated+0.25% sodium gluconate, as strength,absorption, and shrinkage.

FIG. 42 provides a graphic illustration of the effect of cement type oncarbon dioxide uptake in a mortar mix.

FIG. 43 provides a graphic illustration of the effects of temperature ofmaterials on slump, relative to control, in carbonated mortar mixes.Temperatures were 7° C., 15° C. and 25° C.

FIG. 44 provides a graphic illustration of the effect of w/c ratio oncarbon dioxide uptake in a mortar mix.

FIG. 45 provides a graphic illustration of the effect of w/c ratio oncarbon dioxide uptake in a mortar mix.

FIG. 46 provides a graphic illustration of the effect of w/c ratio oncarbon dioxide uptake in a concrete mix.

FIG. 47 provides a graphic illustration of the relationship betweencarbon dioxide uptake and temperature rise in a mortar mix at variousw/c.

FIG. 48 provides a graphic illustration of the relationship betweencarbon dioxide uptake and temperature rise in mortar mixes prepared fromcements from Holcim GU, Lafarge Quebec, and Lehigh, at w/c of 0.5.

FIG. 49 provides a graphic illustration of the effects of sodiumgluconate at 0, 0.1%, or 0.2%, added after carbonation to a concrete mixon slump at 1, 10, and 20 minutes.

FIG. 50 provides a graphic illustration of the effects of fructose oninitial slump of carbonated concrete mix.

FIG. 51 provides a graphic illustration of the effects of fructose on24-hour and 7-day compressive strength in a carbonated concrete mix.

FIG. 52 provides a graphic illustration of the relationship betweensurface area compressive strength at 24 hours of carbonated mortarsproduced with different cements.

FIG. 53 provides a graphic illustration of carbon dioxide dosing (topline), carbon dioxide uptake (second line from top), and carbon dioxidedetected at two sensors (bottom two lines) in a precast mixing operationwhere carbon dioxide flow was adjusted according to the carbon dioxidedetected by the sensors.

FIG. 54 shows isothermal calorimetry curves in mortar prepared withHolcium GU cement carbonated at low levels of carbonation

FIG. 55 shows total heat evolution at various time points in mortarprepared with Holcium GU cement carbonated at low levels of carbonation

FIG. 56 shows set, as represented by penetrometer readings, in mortarprepared with Holcium GU cement carbonated at a low level of carbonation

FIG. 57 shows isothermal calorimetry curves in mortar prepared withLafarge Brookfield GU cement carbonated at low levels of carbonation

FIG. 58 shows 8 hour and 24 hour compressive strengths in mortarprepared with Lafarge Brookfield GU cement carbonated at low levels ofcarbonation

FIG. 59 shows isothermal calorimetry curves in concrete prepared withLafarge Brookfield GU cement carbonated at low levels of carbonation

FIG. 60 shows calorimetry energy curves in concrete prepared withLafarge Brookfield GU cement carbonated at low levels of carbonation

FIG. 61 shows 8 hour and 12 hour compressive strengths in concreteprepared with Lafarge Brookfield GU cement carbonated at low levels ofcarbonation

FIG. 62 shows set, as represented by penetrometer readings, in mortarprepared with Lafarge Brookfield GU cement carbonated at a low level ofcarbonation

FIG. 63 shows 8 hour and 12 hour compressive strengths in concreteprepared with St. Mary's Bowmanville GU cement carbonated at low levelsof carbonation

FIG. 64 shows 12-hour compressive strengths of concrete carbonated atvarious low doses of carbonation

FIG. 65 shows 16-hour compressive strengths of concrete carbonated atvarious low doses of carbonation

FIG. 66 shows 24-hour compressive strengths of concrete carbonated atvarious low doses of carbonation

FIG. 67 shows 7-day compressive strengths of concrete carbonated atvarious low doses of carbonation

FIG. 68 shows carbon dioxide uptake of dry mix concrete at various dosesof sodium gluconate.

FIG. 69 shows compacted cylinder mass (a proxy for density) related tosodium gluconate dose in carbonated and uncarbonated dry mix concrete.

FIG. 70 shows the data of FIG. 69 normalized to control

FIG. 71 shows 6 hour energy released related to sodium gluconate dose incarbonated and uncarbonated dry mix concrete.

FIG. 72 shows the data of FIG. 71 normalized to control

FIG. 73 shows rates of CO₂ uptake in mortars prepared with added CaO,NaOH, or CaCl2, or no additive.

FIG. 74 shows a summary of calorimetry data for mortars prepared withand without added CaO and exposed to carbon dioxide for various lengthsof time while mixing, as well as carbon dioxide uptake.

FIG. 75 shows relative comparison of energy released by mortar mixeswith no added CaO subjected to carbonation, compared to uncarbonatedcontrol

FIG. 76 shows a relative comparison of energy released by CaO-dopedmortar mixes exposed to carbon dioxide for various times, compared tomortar mixes with no added CaO exposed to carbon dioxide for the sametime periods.

DETAILED DESCRIPTION OF THE INVENTION

I. Introduction

The invention provides methods, apparatus, and compositions forproduction of materials comprising a cement binder, e.g., a hydrauliccement or non-hydraulic cement. “Cement mix,” as that term is usedherein, includes a mix of a cement binder, e.g., a hydraulic cement,such as a Portland cement, and water; in some cases, “cement mix”includes a cement binder mixed with aggregate, such as a mortar (alsotermed a grout, depending on consistency), in which the aggregate isfine aggregate; or “concrete,” which includes a coarse aggregate. Thecement binder may be a hydraulic or non-hydraulic cement, so long as itprovides minerals, e.g. calcium, magnesium, sodium, and/or potassiumcompounds such as CaO, MgO, Na₂O, and/or K₂O that react with carbondioxide to produce stable or metastable products containing the carbondioxide, e.g., calcium carbonate. An exemplary hydraulic cement usefulin the invention is Portland cement. In general herein the invention isdescribed in terms of hydraulic cement binder and hydraulic cementmixes, but it will be appreciated that the invention encompsasses anycement mix, whether containing a hydraulic or non-hydraulic cementbinder, so long as the cement binder is capable of forming stable ormetastable products when exposed to carbon dioxide, e.g., containscalcium, magnesium, sodium, and/or potassium compounds such as CaO, MgO,Na₂O, and/or K₂O. In certain embodiments, the invention providesmethods, apparatus, and compositions for production of a cement mix(concrete) containing cement, such as Portland cement, treated withcarbon dioxide. As used herein, the term “carbon dioxide” refers tocarbon dioxide in a gas, solid, liquid, or supercritical state where thecarbon dioxide is at a concentration greater than its concentration inthe atmosphere; it will be appreciated that under ordinary conditions inthe production of cement mixes (concrete mixes) the mix is exposed toatmospheric air, which contains minor amounts of carbon dioxide. Thepresent invention is directed to production of cement mixes that areexposed to carbon dioxide at a concentration above atmosphericconcentrations.

Cement mix operations are commonly performed to provide cement mixes(concrete) for use in a variety of applications, the most common ofwhich is as a building material. Such operations include precastoperations, in which a concrete structure is formed in a mold from thecement mix and undergoes some degree of hardening before transport anduse at a location separate from the mix location, and ready mixoperations, in which the concrete ingredients are supplied at onelocation and generally mixed in a transportable mixer, such as the drumof a ready mix truck, and transported to a second location, where thewet mix is used, typically by being poured or pumped into a temporarymold. Precast operations can be either a dry cast operation or a wetcast operation, whereas ready mix operations are wet cast. Any otheroperation in which a concrete mix is produced in a mixer and exposed tocarbon dioxide during mixing is also subject to the methods andcompositions of the invention.

Without being bound by theory, when the cement mix (concrete) is exposedto carbon dioxide, the carbon dioxide first dissolves in mix water andthen forms intermediate species, before precipitating as a stable ormetastable species, e.g., calcium carbonate. As the carbonate speciesare removed from solution, further carbon dioxide may dissolve in thewater. In certain embodiments, the mix water contains carbon dioxidebefore exposure to the cement binder. All of these processes areencompassed by the term “carbonation” of the cement mix, as that term isused herein.

II. Components of the Invention

In certain embodiments the invention provides methods for preparing amix containing cement, by contacting a mixture of a cement binder, e.g.,hydraulic cement and water, and, optionally, other components such asaggregate (a “cement mix”, or “concrete,” e.g., a “hydraulic cementmix”) with carbon dioxide during some part of the mixing of the cementmix, e.g., hydraulic cement mix.

In certain embodiments, a hydraulic cement is used. The term “hydrauliccement,” as used herein, includes a composition which sets and hardensafter combining with water or a solution where the solvent is water,e.g., an admixture solution. After hardening, the compositions retainstrength and stability even under water. An important characteristic isthat the hydrates formed from the cement constituents upon reaction withwater are essentially insoluble in water. A hydraulic cement used in theinvention may be any hydraulic cement capable of forming reactionproducts with carbon dioxide. The hydraulic cement most commonly used isbased upon Portland cement. Portland cement is made primarily fromlimestone, certain clay minerals, and gypsum, in a high temperatureprocess that drives off carbon dioxide and chemically combines theprimary ingredients into new compounds. In certain embodiments, thehydraulic cement in the hydraulic cement mix is partially or completelycomposed of Portland cement.

A “hydraulic cement mix,” as that term is used herein, includes a mixthat contains at least a hydraulic cement and water. Additionalcomponents may be present, such as aggregates, admixtures, and the like.In certain embodiments the hydraulic cement mix is a concrete mix, i.e.,a mixture of hydraulic cement, such as Portland cement, water, andaggregate, optionally also including an admixture.

The methods in certain embodiments are characterized by contactingcarbon dioxide with wet cement binder, e.g., hydraulic cement, in amixer at any stage of the mixing, such as during mixing of the cementwith water, or during the mixing of wetted cement with other materials,or both. The cement may be any cement, e.g., hydraulic cement capable ofproducing reaction products with carbon dioxide. For example, in certainembodiments the cement includes or is substantially all Portland cement,as that term is understood in the art. The cement may be combined in themixer with other materials, such as aggregates, to form acement-aggregate mixture, such as mortar or concrete. The carbon dioxidemay be added before, during, or after the addition of the othermaterials besides the cement and the water. In addition oralternatively, in certain embodiments the water itself may becarbonated, i.e., contain dissolved carbon dioxide.

In certain embodiments, the contacting of the carbon dioxide with thecement mix, e.g., hydraulic cement mix, may occur when part but not allof the water has been added, or when part but not all of the cement hasbeen added, or both. For example, in one embodiment, a first aliquot ofwater is added to the cement or cement aggregate mixture, to produce acement or cement-aggregate mixture that contains water in a certainwater/cement (w/c) ratio or range of w/c ratios. In some cases one ormore components of the cement mix, e.g., hydraulic cement mix, such asaggregate, may be wet enough that is supplies sufficient water so thatthe mix may be contacted with carbon dioxide. Concurrent with, or after,the addition of the water, carbon dioxide is introduced to the mixture,while the mixture is mixing in a mixer.

The carbon dioxide used in the invention may be of any purity and/orform suitable for contact with cement, e.g., hydraulic cement duringmixing to form reaction products. As described, the carbon dioxide is atleast above the concentration of atmospheric carbon dioxide. Forexample, the carbon dioxide may be liquid, gaseous, solid, orsupercritical, or any combination thereof. In certain embodiments, thecarbon dioxide is gaseous when contacted with the cement, e.g.,hydraulic cement, though it may be stored prior to contact in anyconvenient form, e.g., in liquid form. In alternative embodiments, someor all of the carbon dioxide may be in liquid form and delivered to thecement or cement mix (concrete), e.g., in such a manner as to form amixture of gaseous and solid carbon dioxide; the stream of liquid carbondioxide can be adjusted by, e.g., flow rate and/or orifice selection soas to achieve a desired ratio of gaseous to solid carbon dioxide, suchas ratio of approximately 1:1, or within a range of ratios. The carbondioxide may also be solid when delivered to the concrete, i.e., as dryice; this is useful when a controlled or sustained release of carbondioxide is desired, for example, in a ready mix truck in transit to amix site, or other wet mix operations, as the dry ice sublimates overtime to deliver gaseous carbon dioxide to the mix; the size and shape ofthe dry ice added to the mix may be manipulated to ensure proper doseand time of delivery. The carbon dioxide may also be of any suitablepurity for contact with the cement or cement mix (concrete), e.g.,hydraulic cement during mixing under the specified contact conditions toform reaction products. In certain embodiments the carbon dioxide ismore than 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% pure. Incertain embodiments, the carbon dioxide is more than 95% pure. Incertain embodiments, the carbon dioxide is more than 99% pure. Incertain embodiments, the carbon dioxide is 20-100% pure, or 30-100%pure, or 40-100% pure, or 50-100% pure, or 60-100% pure, or 70-100%pure, or 80-100% pure, or 90-100% pure, or 95-100% pure, or 98-100%pure, or 99-100% pure. In certain embodiments, the carbon dioxide is70-100% pure. In certain embodiments, the carbon dioxide is 90-100%pure. In certain embodiments, the carbon dioxide is 95-100% pure. Theimpurities in the carbon dioxide may be any impurities that do notsubstantially interfere with the reaction of the carbon dioxide with thewet cement mix, e.g., hydraulic cement mix. Commercial sources of carbondioxide of suitable purity are well-known. The gas may be commerciallysupplied high purity carbon dioxide. In this case, the commercial gasmay be sourced from a supplier that processes spent flue gasses or otherwaste carbon dioxide so that sequestering the carbon dioxide in thecement mix, e.g., hydraulic cement mix sequesters carbon dioxide thatwould otherwise be a greenhouse gas emission.

The carbon dioxide is contacted with the cement mix, e.g., hydrauliccement mix during mixing by any suitable route, such as over part or allof the surface of the mixing cement mix, e.g., hydraulic cement mix,under the surface of the cement mix, e.g., hydraulic cement mix, or anycombination thereof.

In certain embodiments, the carbon dioxide is contacted with the cementmix, e.g., hydraulic cement mix during mixing by contact with thesurface of the mixing cement mix, e.g., hydraulic cement mix. Withoutbeing bound by theory, it is believed that the carbon dioxide contactedwith the surface of the cement mix, e.g., hydraulic cement mix dissolvesand/or reacts in the water, and is then subsumed beneath the surface bythe mixing process, which then exposes different cement mix, e.g.,cement mix, to be contacted, and that this process continues for as longas the wetted hydraulic cement is exposed to the carbon dioxide. It willbe appreciated that the process of dissolution and/or reaction maycontinue after the flow of carbon dioxide is halted, since carbondioxide will likely remain in the gas mixture in contact with the cementmix, e.g., hydraulic cement mix. In embodiments in which liquid carbondioxide is used to produce gaseous and solid carbon dioxide, the solidcarbon dioxide will sublimate and continue to deliver gaseous carbondioxide to the cement mix, e.g., hydraulic cement mix after the flow ofliquid carbon dioxide has ceased. This is particularly useful in readymix truck operations, where there may be insufficient time at thebatching facility to allow uptake of the desired amount of carbondioxide; the use of liquid carbon dioxide which converts to gaseous andsolid carbon dioxide allow more carbon dioxide to be delivered to themix even after the truck leaves the batching facility. Other methods ofincreasing carbon dioxide delivery, such as using carbon dioxide-chargedwater in the mix, may also be used. In addition, or alternatively, solidcarbon dioxide, i.e., dry ice, may be used directly by addition to theconcrete mix. This allows for controlled delivery as the dry icesublimates, as described. For example, dry ice may be added to a cementmix in a ready mix truck. The amount of dry ice added may be enough toprovide a dose of 0.01-5% carbon dioxide bwc, for example, 0.01-1%, or0.01-0.5%, or 0.01-0.2%, or 0.1-2% or 0.1-1%, or 0.2-3%, or 0.5-3%. Thedry ice may be added in one or more batches. The shape of the dry icemay be selected depending on, e.g., the speed of gaseous carbon dioxidedelivery desired; for example, if rapid delivery is desired, the dry icemay be added as small pellets, thus increasing surface/volume ratio forcarbon dioxide sublimation, or if a slower delivery is desired, the dryice may be added as a larger mass, e.g., slab, with a correspondinglysmaller surface/volume ratio and slower sublimation, or any combinationof shapes and masses to achieve the desired dose of carbon dioxide andrate of delivery. The dry ice may be added at any convenient stage inmixing, for example, at the start of mixing or within 5 or 10 minutes ofthe start of mixing, or later in the mixing, for example, as a ready mixtruck approaches a job site or the time of delivery of its concreteload. In addition, solid carbon dioxide may be added before or after afirst, second, or third addition of water where water addition to theconcrete mix is divided into two or more doses. Mixing speed for theconcrete mix may also be modulated to achieve a desired rate of dosingor other desired results. For example, in certain embodiments, theinvention provides a method for delivering carbon dioxide to concretemixing in a ready mix truck by adding solid carbon dioxide to theconcrete mix during the mixing, where at least 20, 30, 40, 50, 60, 70,80, 90, 95, or 99% of the carbon dioxide delivered to the concrete isadded in the form of solid carbon dioxide.

In embodiments in which carbon dioxide is contacted with the surface ofthe cement mix, e.g., hydraulic cement mix, the flow of carbon dioxidemay be directed from an opening or plurality of openings (e.g., manifoldor conduit opening) that is at least 5, 10, 30, 50, 80, 100, or morethan 100 cm from the surface of the cement mix, e.g., hydraulic cementmix during carbon dioxide flow, on average, given that the surface ofthe mix will move with mixing.

In embodiments in which the carbon dioxide is contacted under thesurface of the cement mix, e.g., hydraulic cement mix, any suitablemeans of providing the carbon dioxide may be used. In some embodiments,the flow of carbon dioxide may be both under the surface and over thesurface, either by use of two different openings or plurality ofopenings or by movement of the openings relative to the mix, e.g., underthe surface at one stage and over the surface at another, which may beuseful to prevent clogging of the openings.

The carbon dioxide may be contacted with the cement mix, e.g., hydrauliccement mix such that it is present during mixing by any suitable systemor apparatus. In certain embodiments, gaseous or liquid carbon dioxideis supplied via one or more conduits that contain one or more openingspositioned to supply the carbon dioxide to the surface of the mixingcement mix, e.g., hydraulic cement mix. The conduit and opening may beas simple as a tube, e.g., a flexible tube with an open end. The conduitmay be sufficiently flexible so as to allow for movement of variouscomponents of the cement mix, e.g., hydraulic cement mixing apparatus,the conduit opening, and the like, and/or sufficiently flexible to beadded to an existing system as a retrofit. On the other hand, theconduit may be sufficiently rigid, or tied-off, or both, to insure thatit does not interfere with any moving part of the cement mix, e.g.,hydraulic cement mixing apparatus. In certain embodiments, part of theconduit can be used for supplying other ingredients to the cement mix,e.g., water, and configured such that either the other ingredient orcarbon dioxide flows through the conduit, e . . . , by means of aT-junction.

In certain embodiments, the carbon dioxide exits the conduit or conduitsvia one or more manifolds comprising a plurality of openings. Theopening or openings may be positioned to reduce or eliminate clogging ofthe opening with the cement mix, e.g., hydraulic cement mix. Themanifold is generally connected via the conduit to at least one fluid(gas or liquid) supply valve, which governs flow of pressurized fluidbetween a carbon dioxide source, e.g. a pressurized gas or liquidsupply, and the manifold. In some embodiments, the fluid supply valvemay include one or more gate valves that permit the incorporation ofcalibration equipment, e.g., one or more mass flow meters.

The mass of carbon dioxide provided to the cement mix, e.g., hydrauliccement mix via the conduit or conduits may be controlled by a mass flowcontroller, which can modulate the fluid supply valve, e.g., close thevalve to cease supply of carbon dioxide fluid (liquid or gas).

Carbon dioxide may also be delivered to the cement mix, e.g., hydrauliccement mix as part of the mix water, i.e., dissolved in some or all ofthe mix water. Methods of charging water with carbon dioxide arewell-known, such as the use of technology available in the sodaindustry. Some or all of the carbon dioxide to be used may be deliveredthis way. The mix water may be charged to any desired concentration ofcarbon dioxide achievable with the available technology, such as atleast 2, 4, 6, 8, 10 g of carbon dioxide/L of water, or 2-12, 2-10,4-12, 4-10, 6-12, 6-10, 8-12, or 8-10 g of carbon dioxide/L of water.Without being bound by theory, it is thought that the mix water socharged contacts the cement mix, e.g., hydraulic cement mix and thecarbon dioxide contained therein reacts very quickly with components ofthe cement mix, e.g., hydraulic cement mix, leaving the water availableto dissolve additional carbon dioxide that may be added to the system,e.g., in gaseous form.

The carbon dioxide is supplied from a source of carbon dioxide, such as,in the case of gaseous carbon dioxide, a pressurized tank filled withcarbon dioxide-rich gas, and a pressure regulator. The tank may bere-filled when near empty, or kept filled by a compressor. The regulatormay reduce the pressure in the tank to a maximum feed pressure. Themaximum feed pressure may be above atmospheric, but below supercriticalgas flow pressure. The feed pressure may be, for example, in a rangefrom 120 to 875 kPa. A pressure relief valve may be added to protect thecarbon dioxide source components. The carbon dioxide supplied by thecarbon dioxide source may be about room temperature, or it may bechilled or heated as desired. In certain embodiments, some or all of thecarbon dioxide is supplied as a liquid. In some cases the liquid isconverted to gas beore delivery to the mixer; in other cases, theremains a liquid in storage and movement to the mixer, and when releasedat the mixer forms a mixture comprising solid and gaseous carbondioxide. In the latter case, one or more pressure sensors may be used;e.g., for the nozzle system to control dry ice formation between thenozzle and solenoid as well as to confirm pre-solenoid pressure ismaintained to ensure the line remains liquid.

Carbon dioxide may be introduced to the mixer such that it contacts thehydraulic cement mix before, during, or after addition of water, or anycombination thereof, so long as it is present during some portion of themixing of some or all of the cement mix, e.g., hydraulic cement mix. Incertain embodiments, the carbon dioxide is introduced during a certainstage or stages of mixing. In certain embodiments, the carbon dioxide isintroduced to a cement mix, e.g., hydraulic cement mix during mixing atone stage only. In certain embodiments, the carbon dioxide is introducedduring one stage of water addition, followed by a second stage of wateraddition. In certain embodiments, the carbon dioxide is introduced toone portion of cement mix, e.g., hydraulic cement mix, followed byaddition of one or more additional portions of cement mix, e.g.,hydraulic cement mix.

In certain embodiments, the carbon dioxide is introduced into a firststage of mixing of water in the cement mix, e.g., hydraulic cement mix,then, after this stage, additional water is added without carbondioxide. For example, water may be added to a cement mix, e.g.,hydraulic cement mix, e.g., a Portland cement mix, until a desired w/cratio is achieved, then carbon dioxide may be contacted during mixing ofthe cement mix, e.g., hydraulic cement mix for a certain time at acertain flow rate or rates (or as directed by feedback, describedfurther herein), then after carbon dioxide flow has stopped, additionalwater may be added in one or more additional stages to reach a desiredw/c content, or a desired flowability, in the cement mix, e.g.,hydraulic cement mix. The cement mixes contain aggregates, and it willbe appreciated that the available aggregate may already have a certainwater content and that little or no additional water need be added toachieve the desired w/c ratio for the first stage and that, in someenvironments, it may not be possible to achieve the desired w/c ratiobecause aggregate may be too wet, in which case the closest w/c ratio tothe optimum is achieved. In certain embodiments, the w/c ratio for thefirst stage is less than 0.5, or less than 0.4, or less than 0.3, orless than 0.2, or less than 0.18, or less than 0.16, or less than 0.14,or less than 0.12, or less than 0.10, or less than 0.08, or less than0.06. In certain embodiments, the w/c ratio for the first stage is lessthan 0.4. In certain embodiments, the w/c ratio for the first stage isless than 0.3. In certain embodiments, the w/c ratio for the first stageis less than 0.2. In certain embodiments, the w/c ratio for the firststage is less than 0.18. In certain embodiments, the w/c ratio for thefirst stage is less than 0.14. In certain embodiments, the w/c ratio forthe first stage is 0.04-0.5, or 0.04-0.4, or 0.04-0.3, or 0.04-0.2, or0.04-0.18, or 0.04-0.16, or 0.04-0.14, or 0.04-0.12, or 0.04-0.10, or0.04-0.08. In certain embodiments, the w/c ratio for the first stage is0.06-0.5, or 0.06-0.4, or 0.06-0.3, or 0.06-0.24, or 0.06-0.22, or0.06-0.2, or 0.06-0.18, or 0.06-0.16, or 0.06-0.14, or 0.06-0.12, or0.06-0.10, or 0.06-0.08. In certain embodiments, the w/c ratio for thefirst stage is 0.08-0.5, or 0.08-0.4, or 0.08-0.3, or 0.08-0.24, or0.08-0.22, or 0.08-0.2, or 0.08-0.18, or 0.08-0.16, or 0.08-0.14, or0.08-0.12, or 0.08-0.10. In certain embodiments, the w/c ratio for thefirst stage is 0.06-0.3. In certain embodiments, the w/c ratio for thefirst stage is 0.06-0.2. In certain embodiments, the w/c ratio for thefirst stage is 0.08-0.2. Addition of additional water in subsequentstages to the first stage, when, in general, no further carbon dioxideis introduced, may be done to achieve a certain final w/c ratio, or toachieve a certain flowability. For example, for a ready-mix truck, acertain amount of water is added to the mixture at the ready-mixproduction site, then further water may be added at the work site toachieve proper flowability at the work site. Flowability may be measuredby any suitable method, for example, the well-known slump test.

In some embodiments, carbon dioxide is added during mixing to a portionof a cement mix, e.g., hydraulic cement mix in one stage, thenadditional portions of materials, e.g., further cement mix, e.g.,hydraulic cement mix, are added in one or more additional stages.

The carbon dioxide, e.g., gaseous carbon dioxide or liquid carbondioxide, is introduced in the mixing cement mix, e.g., hydraulic cementmix, for example, in the first stage of mixing, at a certain flow rateand for a certain duration in order to achieve a total carbon dioxideexposure. The flow rate and duration will depend on, e.g., the purity ofthe carbon dioxide gas, the total batch size for the cement mix, e.g.,hydraulic cement mix and the desired level of carbonation of the mix. Ametering system and adjustable valve or valves in the one or moreconduits may be used to monitor and adjust flow rates. In some cases,the duration of carbon dioxide flow to provide exposure is at or below amaximum time, such as at or below 100, 50, 20, 15, 10, 8, 5, 4, 3, 2, orone minute. In certain embodiments, the duration of carbon dioxide flowis less than or equal to 5 minutes. In certain embodiments, the durationof carbon dioxide flow is less than or equal to 4 minutes. In certainembodiments, the duration of carbon dioxide flow is less than or equalto 3 minutes. In certain embodiments, the duration of carbon dioxideflow is less than or equal to 2 minutes. In certain embodiments, theduration of carbon dioxide flow is less than or equal to 1 minutes. Insome cases, the duration of carbon dioxide flow to provide exposure iswithin a range of times, such as 0.5-20 min, or 0.5-15 min, or 0.5-10min, or 0.5-8 min, or 0.5-5 min, or 0.5-4 min, or 0.5-3 min, or 0.5-2min, or 0.5-1 min, or 1-20 min, or 1-15 min, or 1-10 min, or 1-8 min, or1-5 min, or 1-4 min, or 1-3 min, or 1-2 min. In certain embodiments, theduration of carbon dioxide flow is 0.5-5 min. In certain embodiments,the duration of carbon dioxide flow is 0.5-4 min. In certainembodiments, the duration of carbon dioxide flow is 0.5-3 min. Incertain embodiments, the duration of carbon dioxide flow is 1-5 min. Incertain embodiments, the duration of carbon dioxide flow is 1-4 min. Incertain embodiments, the duration of carbon dioxide flow is 1-3 min. Incertain embodiments, the duration of carbon dioxide flow is 1-2 min.

The flow rate and duration of flow may be set or adjusted to achieve adesired level of carbonation, as measured by weight of cement (bwc). Incertain embodiments, the level of carbonation is more than 0.5, 1, 2, 3,4, 5, 6, 7, 8, 9, or 10% bwc. In certain embodiments, the level ofcarbonation is more than 1% by weight. In certain embodiments, the levelof carbonation is more than 2% bwc. In certain embodiments, the level ofcarbonation is more than 3% bwc. In certain embodiments, the level ofcarbonation is more than 4% bwc. In certain embodiments, the level ofcarbonation is more than 5% bwc. In certain embodiments, the level ofcarbonation is more than 6% bwc. In certain embodiments, the level ofcarbonation is 1-20%, or 1-15%, or 1-10%, or 1-8%, or 1-6%, or 1-5%, or1-4%, or 1-3%, or 1-2%, or 2-20%, or 2-15%, or 2-10%, or 2-8%, or 2-6%,or 2-5%, or 2-4%, or 2-3%, or 0.5-20%, or 0.5-15%, or 0.5-10%, or0.5-8%, or 0.5-6%, or 0.5-5%, or 0.5-4%, or 0.5-3%, or 0.5-2%. Incertain embodiments, the level of carbonation is 0.5-3%. In certainembodiments, the level of carbonation is 0.5-2%. In certain embodiments,the level of carbonation is 1-6%. In certain embodiments, the level ofcarbonation is 1-4%. In certain embodiments, the level of carbonation is2-8%. In certain embodiments, the level of carbonation is 2-6%. Incertain embodiments, the level of carbonation is 2-4%. In certainembodiments, the level of carbonation is 3-10%. In certain embodiments,the level of carbonation is 3-8%. In certain embodiments, the level ofcarbonation is 3-6%. In certain embodiments, the level of carbonation is4-10%. In certain embodiments, the level of carbonation is 4-8%. Incertain embodiments, the level of carbonation is 4-6%. In certainembodiments, the level of carbonation is 5-10%. In certain embodiments,the level of carbonation is 5-8%. In certain embodiments, the level ofcarbonation is 5-6%. The level of carbonation may be ascertained by anysuitable method, such as by the standard combustion analysis method,e.g. heating sample and quantifying the composition of the off gas. Aninstrument such as the Eltra CS-800 (KR Analytical, Cheshire, UK), orinstrument from LECO (LECO Corporation, St. Joseph, Mich.) may be used.

It will be appreciated that the level of carbonation also depends on theefficiency of carbonation, and that inevitably some of the carbondioxide delivered to the mixing cement mix will be lost to theatmosphere; thus, the actual amount of carbon dioxide delivered can beadjusted based on the expected efficiency of carbonation. Thus for allthe desired levels of carbonation as listed, an appropriate factor maybe added to determine the amount of carbon dioxide that must bedelivered as a dose to the cement mix; e.g., if the expected efficiencyis 50% and the desired carbonation level is 1% bwc, then a dose of 2%bwc would be delivered to the mix. Appropriate doses may be calculatedfor desired carbonations at an efficiency of 5, 10, 20, 30, 40, 50, 60,65, 70, 75, 80, 85, 90, 95, 96, 97, 98, or 99%.

In certain embodiments, a relatively low level of carbonation is used,e.g., a level of carbonation below 1%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%,0.3%, 0.2%, or 0.1% bwc. For example, it has been found that certainproperties, e.g., early strength development and set, may be acceleratedin cement mixes, such as hydraulic cement mixes, that are exposed torelatively low levels of carbon dioxide during mixing. It is possiblethat, in some cases, the exposure may be low enough that the degree ofcarbonation is not measurably above that of a similar cement mix thathas not been exposed to carbon dioxide; nonetheless, the exposure maylead to the desired enhanced properties. Thus, in certain embodiments,the mixing cement mix is exposed to a certain relatively low dose ofcarbon dioxide (in some cases regardless of final carbonation value); inthis sense, carbon dioxide is used like an admixture whose finalconcentration in the cement mix is not important but rather its effectson the properties of the mix. In certain embodiments, the mix may beexposed to a dose of carbon dioxide of less than 1.5%, 1.2%, 1%, 0.8%,0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, or 0.05% bwc, or a dose of0.01-1.5%, 0.01-1.2%, 0.01-1%, 0.01-0.8%, 0.01-0.6%, 0.01-0.5%,0.01-0.4%, 0.01-0.3%, 0.01-0.2%, or 0.01-0.1% bwc, or a dose of0.02-1.5%, 0.02-1.2%, 0.02-1%, 0.02-0.8%, 0.02-0.6%, 0.02-0.5%,0.02-0.4%, 0.02-0.3%, 0.02-0.2%, or 0.02-0.1% bwc, or a dose of0.04-1.5%, 0.04-1.2%, 0.04-1%, 0.04-0.8%, 0.04-0.6%, 0.04-0.5%,0.04-0.4%, 0.04-0.3%, 0.04-0.2%, or 0.04-0.1% bwc, or a dose of0.06-1.5%, 0.06-1.2%, 0.06-1%, 0.06-0.8%, 0.06-0.6%, 0.06-0.5%,0.06-0.4%, 0.06-0.3%, 0.06-0.2%, or 0.06-0.1% bwc, or a dose of0.1-1.5%, 0.1-1.2%, 0.1-1%, 0.1-0.8%, 0.1-0.6%, 0.1-0.5%, 0.1-0.4%,0.1-0.3%, or 0.1-0.2% bwc. The choice of exposure level will depend onfactors such as efficiency of carbonation in the process being used,degree of modulation of one or more properties desired (e.g., earlystrength development or early set), type of operation (e.g., dry castvs. wet cast), and type of cement, as different types of cement mayproduce mixes with different degrees of modulation with a given carbondioxide exposure. If an unfamiliar cement or mix type is being used,preliminary work may be done to find one or more suitable carbon dioxidedoses to produce the desired results. Especially in the case ofaccelerated strength and/or set development, the use of an appropriatedose of carbon dioxide can allow work to progress faster, e.g., verticalpours may move upward more quickly, surfaces may be finished earlier,molds removed earlier, and the like.

The methods and compositions of the invention allow for very high levelsof efficiency of uptake of carbon dioxide into the mixing concrete,where the efficiency of uptake is the ratio of carbon dioxide thatremains in the mixing concrete as stable reaction products to the totalamount of carbon dioxide to which the mixing concrete is exposed. Incertain embodiments, the efficiency of carbon dioxide uptake is at least40, 50, 60, 70, 80, 90, 95, 96, 97, 98, 99, or 99.%, or 40-100, 50-100,60-100, 70-100, 80-100, 90-100, 40-99, 50-99, 60-99, 70-99, 80-99, or90-99%.

In a wet cast operation, the addition of carbon dioxide, components ofthe cement mix, e.g., hydraulic cement mix, such as one or moreadmixtures, described more fully below, may be adjusted so thatflowability of the final cement mix, e.g., hydraulic cement mix iswithin 10% of the flowability that would be achieved without theaddition of carbon dioxide. In certain embodiments, the addition ofcarbon dioxide, components of the cement mix, e.g., hydraulic cementmix, such as one or more admixtures, described more fully below, areadjusted so that flowability of the final cement mix, e.g., hydrauliccement mix is within 50, 40, 30, 20 15, 10, 8, 5, 4, 3, 2, or 1% of theflowability that would be achieved without the addition of carbondioxide, or of a predetermined flowability. In certain embodiments, theaddition of carbon dioxide, components of the cement mix, e.g.,hydraulic cement mix, such as one or more admixtures, described morefully below, are adjusted so that flowability of the final cement mix,e.g., hydraulic cement mix is within 20% of the flowability that wouldbe achieved without the addition of carbon dioxide, or a predeterminedflowability. In certain embodiments, the addition of carbon dioxide,components of the cement mix, e.g., hydraulic cement mix, such as one ormore admixtures, described more fully below, are adjusted so thatflowability of the final cement mix, e.g., hydraulic cement mix iswithin 10% of the flowability that would be achieved without theaddition of carbon dioxide, or a predetermined flowability. In certainembodiments, the addition of carbon dioxide, components of the cementmix, e.g., hydraulic cement mix, such as one or more admixtures,described more fully below, are adjusted so that flowability of thefinal cement mix, e.g., hydraulic cement mix is within 5% of theflowability that would be achieved without the addition of carbondioxide, or a predetermined flowability. In certain embodiments, theaddition of carbon dioxide, components of the cement mix, e.g.,hydraulic cement mix, such as one or more admixtures, described morefully below, are adjusted so that flowability of the final cement mix,e.g., hydraulic cement mix is within 2% of the flowability that would beachieved without the addition of carbon dioxide, or a predeterminedflowability. In certain embodiments, the addition of carbon dioxide,components of the cement mix, e.g., hydraulic cement mix, such as one ormore admixtures, described more fully below, are adjusted so thatflowability of the final cement mix, e.g., hydraulic cement mix iswithin 1-50%, or 1-20%, or 1-10%, or 1-5%, or 2-50%, or 2-20%, or 2-10%,or 2-5% of the flowability that would be achieved without the additionof carbon dioxide, or a predetermined flowability.

A. Admixtures

Admixtures are often used in cement mix, e.g., hydraulic cement mixes,such as concrete mixes, to impart desired properties to the mix.Admixtures are compositions added to a cement mix, e.g., hydrauliccement mix such as concrete to provide it with desirable characteristicsthat are not obtainable with basic cement mix, e.g., hydraulic cementmixes, such as concrete mixtures or to modify properties of the cementmix, e.g., hydraulic cement mix, i.e., concrete to make it more readilyuseable or more suitable for a particular purpose or for cost reduction.As is known in the art, an admixture is any material or composition,other than the hydraulic cement, aggregate and water, that is used as acomponent of the cement mix, e.g., hydraulic cement mix, such asconcrete or mortar to enhance some characteristic, or lower the cost,thereof. In some instances, the desired cement mix, e.g., hydrauliccement mix, e.g., concrete performance characteristics can only beachieved by the use of an admixture. In some cases, using an admixtureallows for the use of less expensive construction methods or designs,the savings from which can more than offset the cost of the admixture.

In certain embodiments, the carbonated cement mix, e.g., hydrauliccement mixture, e.g., concrete, may exhibit enhanced characteristicswhen compared with the same mixture that was not exposed to carbondioxide. This can depend on the type of cement used in the carbonatedcement mix and/or the dose of carbon dioxide used and final carbonationachieved. In this sense, carbon dioxide can itself act as an admixture.For example, in certain embodiments, the carbonated cement mix, e.g.,concrete mixture, has superior properties such as greater strength, suchas greater 1-, 7-, or 28-day strength, e.g., at least 1, 2, 3, 4, 5, 7,10, 15, 20, 30, or 40% greater strength than the non-carbonated concretemixture at 1-, 7-, or 28-days. In general herein, “strength” refers tocompressive strength, as that term is generally understood in the art.In certain embodiments, the carbonated cement mix, e.g. concrete, mayexhibit accelerated set compared to non-carbonated mix, such as a fastertime to initial set (for example, penetrometer measurment of 500 psiaccording to ASTM C403) or a faster time to final set (for example,penetrometer measurment of 4000 psi according to ASTM C403), or both,such as less than 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 40, 30, or 20%of the initial or final set time compared to uncarbonated mix.Carbonated cement mix, e.g., hydraulic cement mixes may also providefinal concrete mixtures that have lower water absorption as compared tonon-carbonated, such as at least 1, 2, 3, 4, 5, 7, 10, 15, 20, 30, or40% lower water absorption. The carbonated cement mix, e.g., hydrauliccement mix, i.e., concrete, may also produce a final product that islower in density but of comprable strength compared to non-carbonated,such as at least 1, 2, 3, 4, 5, 7, 10, 15, 20, 30, or 40% lower densitywith a compressive strength within 1, 2, 3, 4, 5, 7, 10, 15, or 20% ofthe non-carbonated, e.g., at least 5% lower density with a compressivestrength within 2%.

However, depending on the mix design, the carbonated cement mix, e.g.,hydraulic cement mixture, i.e., concrete, may alternatively or inaddition, exhibit properties that it is desired to modulate, such as bythe addition of an admixture. For example, carbonated cement mix, e.g.,hydraulic cement mix for use in a wet cast operation may haveworkability/flow characteristics that are not optimum for a wet castoperation without addition of an admixture or other manipulation of themix, e.g., addition of extra water. As another example, carbonated mixesmay have strength characteristics, e.g., compressive strength at one ormore time points, that are not optimum without addition of an admixtureor other manipulation of the mix. In some cases, the mix design willalready call for an admixture, whose effect on the properties of the mixmay be affected by the carbonation, requiring coordination of the timingof the admixture in relation to the carbon dioxide addition, or othermanipulation. In addition, an admixture may be used to modulate one ormore aspects of the carbonation itself, for example, to increase therate of uptake of the carbon dioxide.

Concrete may be used in wet cast operations, such as in certain precastoperations or in ready mix trucks that transport the concrete to a jobsite where it is used, e.g., poured into molds or otherwise used at thesite, or in dry cast operations, which are precast operations. In thecase of a wet cast operation, the flowability of the concrete should bemaintained at a level compatible with its use in the operation, e.g., inthe case of a ready mix truck, at the job site; whereas for a dry castoperation concrete that does not flow (zero slump) is desirable. In bothdry cast and wet cast operations, strength, e.g., compressive strength,is important, both in the short term so that the concrete can be allowedto stand alone, e.g., molds can be removed, cast objects can bemanipulated, etc., in the shortest possible time, and also in the longterm so that a required final strength is reached. Flowability of a mixmay be evaluated by measuring slump; strength may be evaluated by one ormore strength tests, such as compressive strength. Other properties thatmay be affected by carbonation; in some cases the effect is a positiveone, but if the effect is a negative one, corrected through the use ofone or more admixtures. Such properties include shrinkage and waterabsorption.

In certain cases carbonation of the cement mix, e.g., hydraulic cementmix may affect flowability of a cement mix, e.g., hydraulic cement mix,i.e., a concrete mix, to be used in a wet cast operation, such as in aready mix truck transporting the mix to a job site. Thus in certainembodiments in which a carbonated mix is produced (such as for use witha readymix truck), one or more admixtures may be added to modulate theflowability of the carbonated mixture, either before, during, or aftercarbonation, or any combination thereof, such that it is within acertain percentage of the flowability of the same mixture withoutcarbonation, or of a certain predetermined flowability. The addition ofcarbon dioxide, components of the mix, e.g., concrete mix, and/oradditional components such as one or more admixtures, may be adjusted sothat flowability of the final mix is within 50, 40, 30, 20, 10, 8, 5, 4,3, 2, 1, 0.5, or 0.1% of the flowability that would be achieved withoutthe addition of carbon dioxide, or of a certain predeterminedflowability. In certain embodiments, the addition of carbon dioxide,components of the mix, and/or additional components such as one or moreadmixtures, may be adjusted so that flowability of the final mix iswithin 20% of the flowability that would be achieved without theaddition of carbon dioxide, or within 20% of a predetermined desiredflowability. In certain embodiments, the addition of carbon dioxide,components of the mix, and/or additional components such as one or moreadmixtures, may be adjusted so that flowability of the final mix iswithin 10% of the flowability that would be achieved without theaddition of carbon dioxide, or within 10% of a predetermined desiredflowability. In certain embodiments, the addition of carbon dioxide,components of the mix, and/or additional components such as one or moreadmixtures, may be adjusted so that flowability of the final mix iswithin 5% of the flowability that would be achieved without the additionof carbon dioxide, or within 5% of a predetermined desired flowability.In certain embodiments, the addition of carbon dioxide, components ofthe mix, and/or additional components such as one or more admixtures,may be adjusted so that flowability of the final mix is within 2% of theflowability that would be achieved without the addition of carbondioxide, or within 2% of a predetermined desired flowability. Anysuitable measurement method for determining flowability may be used,such as the well-known slump test. Any suitable admixture may be used,as described herein, such as carbohydrates or carbohydrate derivatives,e.g., fructose, sucrose, glucose, sodium glucoheptonate, or sodiumgluconate, such as sodium glucoheptonate or sodium gluconate.

In certain embodiments, one or more admixtures may be added to modulatethe mix so that a desired strength, either early strength, latestrength, or both, may be achieved. Strength of the carbonated cementmix can be dependent on mix design, thus, although with some mix designscarbonation may increase strength at one or more time points, in othermix designs carbonation may decrease strength at one or more timepoints. See Examples for various mix designs in which carbonationincreased or decreased strength at one or more time points. In somecases, carbonation decreases strength at one or more time points and itis desired to return the strength at the time point to within a certainacceptable limit. In certain cases, one or more admixtures is added toincrease strength byond that seen in non-carbonated concrete of the samedensity. This may be done, e.g., to produce a lightweight concrete withstrength comparable to the denser, non-carbonated concrete. In othercases, one or more admixtures added to a carbonated cement itself causesor exacerbates strength loss, and it is desired to recover the loss.Thus, in certain embodiments an admixture is added to the carbonatedmix, either before, during, or after carbonation, or a combinationthereof, under conditions such that the carbonated mix exhibitsstrength, e.g., 1-, 7-, 28 and/or 56-day compressive strength, within adesired percentage of the strength of the same mix without carbonation,or of a predetermined strength, e.g., within 50, 40, 30, 20, 15, 12, 10,9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1%. In certain embodiments, theaddition of carbon dioxide, components of the mix, and/or additionalcomponents such as one or more admixtures, may be adjusted so thatstrength at a given time point of the final mix is within 20% of thestrength that would be achieved without the addition of carbon dioxide,or within 20% of a predetermined desired strength. In certainembodiments, the addition of carbon dioxide, components of the mix,and/or additional components such as one or more admixtures, may beadjusted so that strength at a given time point of the final mix iswithin 10% of the strength that would be achieved without the additionof carbon dioxide, or within 10% of a predetermined desired strength. Incertain embodiments, the addition of carbon dioxide, components of themix, and/or additional components such as one or more admixtures, may beadjusted so that strength at a given time point of the final mix iswithin 5% of the strength that would be achieved without the addition ofcarbon dioxide, or within 5% of a predetermined desired strength. Incertain embodiments, the addition of carbon dioxide, components of themix, and/or additional components such as one or more admixtures, may beadjusted so that strength at a given time point of the final mix iswithin 2% of the strength that would be achieved without the addition ofcarbon dioxide, or within 2% of a predetermined desired strength. Incertain embodiments the strength is a compressive strength. Any suitablemethod to test strength, such as flexural or compressive strength, maybe used so long as the same test is used for samples with and withoutcarbonation; such tests are well known in the art. Any suitableadmixtures to achieve the desired strengths may be used, such as theadmixtures described herein.

Other properties, such as water absorption, shrinkage, chloridepermeability, and the like, may also be tested and adjusted in a similarmanner, and to similar percentages, as for flowability and/or shrinkage.

It will be appreciated that more than one admixture may be used, forexample, 2, 3, 4, 5, or more than 5 admixtures. For example, certainadmixtures have desirable effects on flowability but undesirable effectson strength development; when such an admixture is used, a secondadmixture that accelerates strength development may also be used.

Any suitable admixture that has the desired effect on the property orproperties of the carbonated cement that it is desired to modified maybe used. TABLE 1 lists exemplary classes and examples of admixtures thatcan be used in the invention, e.g., to modulate the effects ofcarbonation.

TABLE 1 Admixtures for use with carbonated cement Cement Chemical ClassSub Class Application Examples Saccharides Sugars Retarder Fructose,glucose, sucrose Sugar Acids/bases Retarder Sodium Gluconate, sodiumglucoheptonate Organic Polymers Polycarboxylic Plasticizer Manycommercial brands Ethers Sulfonated Plasticizer Many commercial brandsNapthalene Formaldehyde Sulphonated Plasticizer Many commercial brandsMelamine formaldehyde Ligno sulphonates Plasticizer Many commercialbrands Inorganic Salts Alkaline Earth Accelerant Ca(NO₃)₂, Mg(OH)₂ MetalContaining Alkali Metal Accelerant NaCl, KOH Containing Carbonate —NaHCO₃, Na₂CO₃ containing Alkanolamines Tertiary Accelerants/GrindingTriethanolamine, alkanolamines aids Triisopropylamine Phosphonates —Retarders Nitrilotri(methylphosphonic acid), 2-phosphonobutane-1,2,4-tricarboxylic acid Surfactants Vinsol Resins, Air Entraining Manycommercial brands synthetic Agents surfactants Chelating Agents VariousRetarders EDTA, Citric Acid, Chemistries nitrilotriacetic acid

In certain embodiments, one or admixtures is added to a cement mix,e.g., hydraulic cement mix, before, during, or after carbonation of themix, or a combination thereof, where the admixture is a set retarder,plasticizer, accelerant, or air entraining agent. Where it is desired tomodulate flowability, set retarders and plasticizers are useful. Whereit is desired to modulate strength development, accelerants are useful.If it is desired to increase the rate of carbon dioxide uptake, certainair entraining agents may be useful.

Set retarders include carbohydrates, i.e., saccharides, such as sugars,e.g., fructose, glucose, and sucrose, and sugar acids/bases and theirsalts, such as sodium gluconate and sodium glucoheptonate; phosphonates,such as nitrilotri(methylphosphonic acid),2-phosphonobutane-1,2,4-tricarboxylic acid; and chelating agents, suchas EDTA, Citric Acid, and nitrilotriacetic acid. Other saccharides andsaccharide-containing admixes of use in the invention include molassesand corn syrup. In certain embodiments, the admixture is sodiumgluconate. Other exemplary admixtures that can be of use as setretarders include sodium sulfate, citric acid, BASF Pozzolith XR, firmedsilica, colloidal silica, hydroxyethyl cellulose, hydroxypropylcellulose, fly ash (as defined in ASTM C618), mineral oils (such aslight naphthenic), hectorite clay, polyoxyalkylenes, natural gums, ormixtures thereof, polycarboxylate superplasticizers, naphthalene HRWR(high range water reducer). Additional set retarders that can be usedinclude, but are not limited to an oxy-boron compound, lignin, apolyphosphonic acid, a carboxylic acid, a hydroxycarboxylic acid,polycarboxylic acid, hydroxylated carboxylic acid, such as fumaric,itaconic, malonic, borax, gluconic, and tartaric acid, lignosulfonates,ascorbic acid, isoascorbic acid, sulphonic acid-acrylic acid copolymer,and their corresponding salts, polyhydroxysilane, polyacrylamide.Illustrative examples of retarders are set forth in U.S. Pat. Nos.5,427,617 and 5,203,919, incorporated herein by reference.

Accelerants include calcium-containing compounds, such as CaO, Ca(NO₂)₂,Ca(OH)₂, calcium stearate, or CaCl₂, and magnesium-containing compounds,such as magnesium hydroxide, magnesium oxide, magnesium chloride, ormagnesium nitrate. Without being bound by theory, it is thought that, inthe case of carbonated cement, the added calcium or magnesium compoundmay provide free calcium or magnesium to react with the carbon dioxide,providing a sink for the carbon dioxide that spares the calcium in thecement mix, or providing a different site of carbonation than that ofthe cement calcium, or both, thus preserving early strength development.In certain embodiments, CaO (lime) may be added to the mix, or ahigh-free lime cement may be the preferred cement for the mix. Forexample, in certain embodiments, the free lime (CaO) content of thecement used in a particular cement mixture, such as mortar or concrete,may be increased by the addition of CaO to the mixture, generally beforethe mixture is exposed to carbon dioxide, such as by addition of0.01-50%, or 0.01-10%, or 0.01-5%, or 0.01-3%, or 0.01-2%, or 0.01-1%CaO, or 0.1-50%, or 0.1-10%, or 0.1-5%, or 0.1-3%, or 0.1-2%, or 0.1-1%,or 0.2-50%, or 0.2-10%, or 0.2-5%, or 0.2-3%, or 0.2-2% CaO, or 0.2-1%,or 0.5-50%, or 0.5-10%, or 0.5-5%, or 0.5-3%, or 0.5-2% CaO, or 0.5-1%CaO bwc. Alternatively, CaO may be added so that the overall CaO contentof the cement mixture reaches a desired level, such as 0.5-10%, or0.5-5%, or 0.5-3%, or 0.5-2%, or 0.5-1.5%, or at least 0.5, 0.6, 0.7,0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.2,2.5, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10%, 20%, 30%, 40%, or 50% CaObwc. The added CaO will generally also increase the rate of uptake ofcarbon dioxide by the mix during mixing, thus allowing a greater carbondioxide uptake for a given time of exposure, or a lower time of exposureto achieve a given level of uptake. Other set accelerators include, butare not limited to, a nitrate salt of an alkali metal, alkaline earthmetal, or aluminum; a nitrite salt of an alkali metal, alkaline earthmetal, or aluminum; a thiocyanate of an alkali metal, alkaline earthmetal or aluminum; an alkanolamine; a thiosulfate of an alkali metal,alkaline earth metal, or aluminum; a hydroxide of an alkali metal,alkaline earth metal, or aluminum; a carboxylic acid salt of an alkalimetal, alkaline earth metal, or aluminum (preferably calcium formate); apolyhydroxylalkylamine; a halide salt of an alkali metal or alkalineearth metal (e.g., chloride).

The admixture or admixtures may be added to any suitable finalpercentage (bwc), such as in the range of 0.01-0.5%, or 0.01-0.3%, or0.01-0.2%, or 0.01-0.1%, or 0.01-1.0%, or 0.01-0.05%, or 0.05% to 5%, or0.05% to 1%, or 0.05% to 0.5%, or 0.1% to 1%, or 0.1% to 0.8%, or 0.1%to 0.7% per weight of cement. The admixture may be added to a finalpercentage of greater than 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07,0.08, 0.09, 0.1, 0.15, 0.2, 0.3, 0.4, or 0.5%; in certain cases alsoless than 5, 4, 3, 2, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1,0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, or 0.02%.

It has been observed that the timing of addition of a given admixturerelative to carbonation of a cement mix, e.g., hydraulic cement mix mayalter the effects of the admixture on the properties of the cement mix,e.g., hydraulic cement mix, e.g., effects on flowability or strength.For example, in certain mix designs, the addition of sodium gluconateafter carbonation restores flowability to desired levels, but mayadversely affect early strength development; whereas the addition ofsodium gluconate before carbonation maintains early strength developmentbut does not optimally restore flowability. As another example, in mixdesigns in which an air entrainer is desired, it has been found that ifthe air entrainer is added before carbonation, the density of the mix isincreased compared to if the air entrainer is added after carbonation.The admixture or admixtures thus may be added before, during, or aftercarbonation of the cement mix, e.g., hydraulic cement mix, or anycombination thereof. For example, in certain embodiments, the admixtureis added after carbonation; in other embodiments, the admixture is addedbefore carbonation; in yet other embodiments, the admixture is added intwo split doses, one before carbonation and one during and/or aftercarbonation. It will be apparent that if more than one admixture isused, one may be added at one time while another is added at anothertime, for example, in a mix where an air entrainer is used and sodiumgluconate is also added to affect flowability, the sodium gluconate maybe added in split doses, one before carbonation and one during/aftercarbonation, and the air entrainer may be added after carbonation. Thelatter is exemplary only, and any suitable combination of admixtures andtiming to achieve the desired effect or effects may be used.

It has been observed that the effects of carbonation and of admixtureson carbonated cement mix, e.g., hydraulic cement mixes is highlymix-specific. In some cases carbonation actually improves the propertiesof a mix, especially in dry cast situations where flowability is not anissue, and no admixture is required. In other cases, especially in wetcast situations where flowability is an issue, one or more admixturesmay be required to restore one or more properties of the mix. Whether ornot admixture is added, and/or how much is added, to a given batch maybe determined by pre-testing the mix to determine the properties of thecarbonated mix and the effects of a given admixture. In some cases theadmixture and/or amount may be predicted based on previous tests, or onproperties of the cement used in the mix, or on theoreticalconsiderations. It has been found that different cements have differentproperties upon carbonation, and also react differently to a givenadmixture, and the invention includes the use of a library of data onvarious cement types and admixtures so as to predict a desiredadmixture/amount for a mix design, which may be a mix that is the sameas or similar to a mix in the library, or a new mix whose properties canbe predicted from the library. In addition, for a given batch, rheology(flowability) may be monitored during the carbonation of the batch andthe exact timing and/or amount of admixture added to that particularbatch, or to subsequent batches, may be adjusted based on the feedbackobtained. A combination of predicted value for admixture type, timing,and/or amount, and modification of the value based on real-timemeasurements in a given batch or batches may be used.

In certain embodiments, an admixture comprising a carbohydrate orcarbohydrate derivative is added to a cement mix, e.g., hydraulic cementmix before, during, and/or after carbonation of the mix, or acombination thereof. In certain embodiments, the admixture is addedafter carbonation of the cement mix, e.g., hydraulic cement mix, orduring and after carbonation. The carbonation may be accomplished asdescribed herein, for example, by delivering carbon dioxide to thesurface of the cement mix, e.g., hydraulic cement mix during mixing. Thecarbohydrate or derivative may be any carbohydrate as described herein,for example sucrose, fructose, sodium glucoheptonate, or sodiumgluconate. In certain embodiments, the carbohydrate is sodium gluconate.The carbohydrate or derivative, e.g., sodium gluconate may be used at asuitable concentration; in some cases, the concentration is greater than0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.05%, 0.06%, 0.07%,0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.3%, 0.4%, or 0.5% bwc. Theconcentration may also be less than 2, 1.5, 1, 0.9, 0.8, 0.7, 0.6, 0.5,0.4, 0.3, 0.2, or 0.1%. For example, in certain embodiments, sodiumgluconate is used as an admixture at a dose of between 0.01 and 1% bwc,or between 0.01 and 0.8%, or between 0.01 and 0.5%, or between 0.01 and0.4% bwc, or between 0.01 and 0.3%, or between 0.01 and 0.2% bwc, orbetween 0.01 and 0.1%, or between 0.01 and 0.05%, or between 0.03 and 1%bwc, or between 0.03 and 0.8%, or between 0.03 and 0.5%, or between 0.03and 0.4% bwc, or between 0.03 and 0.3%, or between 0.03 and 0.2% bwc, orbetween 0.03 and 0.1%, or between 0.03 and 0.08%, or between 0.05 and 1%bwc, or between 0.05 and 0.8%, or between 0.05 and 0.5%, or between 0.05and 0.4% bwc, or between 0.05 and 0.3%, or between 0.05 and 0.2% bwc, orbetween 0.05 and 0.1%, or between 0.05 and 0.08%, or between 0.1 and 1%bwc, or between 0.1 and 0.8%, or between 0.1 and 0.5%, or between 0.1and 0.4% bwc, or between 0.1 and 0.3%, or between 0.1 and 0.2% bwc. Thesodium gluconate may be added before, during, or after carbonation ofthe mix, or any combination thereof, and may be added as one, two,three, four, or more than four divided doses. The carbohydrate orderivative may be added in two or more doses, such as one dose beforecarbonation and one dose during and/or after carbonation. In certainembodiments, calcium stearate is used as an admixture.

In certain embodiments, a second admixture is also used, such as any ofthe admixtures described herein. In certain embodiments, the secondadmixture is a strength accelerator. In certain embodiments, a thirdadmixture is also used, such as any of the admixtures described herein.In certain embodiments, a fourth admixture is also used, such as any ofthe admixtures described herein.

In certain embodiments, an admixture is used that modulates theformation of calcium carbonate so that one or more polymorphic forms isfavored compared to the mixture without the admixture, e.g., modulatesthe formation of amorphous calcium carbonate, eg., aragonite, orcalcite. Exemplary admixtures of this type include organic polymers suchas polyacrylate and polycarboxylate ether, phosphate esters such ashydroxyamino phosphate ester, phosphonate and phosphonic acids such asnitrilotri(methylphosphonic acid), 2-phosphonobutane-1,2,4-tricarboxylicacid, chelators, such as sodium gluconate, ethylenediaminetetraaceticacid (EDTA), and citric acid, or surfactants, such as calcium stearate.

Other admixtures useful in methods and compositions of the invention aredescribed in U.S. Pat. No. 7,735,274, hereby incorporated by referenceherein in its entirety.

B. Supplementary Cementitious Materials and Cement Replacements

In certain embodiments, one or more supplementary cementitious materials(SCMs) and/or cement replacements are added to the mix at theappropriate stage for the particular SCM or cement replacement. Incertain embodiments, an SCM is used. Any suitable SCM or cementreplacement may be used; exemplary SCMs include blast furnace slag, flyash, silica fume, natural pozzolans (such as metakaolin, calcined shale,calcined clay, volcanic glass, zeolitic trass or tuffs, rice husk ash,diatomaceous earth, and calcined shale), and waste glass. Further cementreplacements include interground limestone, recycled/waste plastic,scrap tires, municipal solid waste ash, wood ash, cement kiln dust,foundry sand, and the like. In certain embodiments, an SCM and/or cementreplacement is added to the mix in an amount to provide 0.1-50%, or1-50%, or 5-50%, or 10-50%, or 20-50%, or 1-40%, or 5-40%, or 10-50%, or20-40% bwc. In certain embodiments, an SCM is used and the SCM is flyash, slag, silica fume, or a naturual pozzolan. In certain embodiment,the SCM is fly ash. In certain embodiments, the SCM is slag.

C. Control Mechanisms

The methods and apparatus of the invention may include one or morecontrol mechanisms, e.g., automatic control mechanisms, to modulate oneor more aspects of the mix and carbonation operation, such as tomodulate the contact of the cement mix, e.g., hydraulic cement mix withcarbon dioxide and/or other components, such as one or more admixturesor water, as well as other aspects of the operation of the mixer, suchas worker safety requirements, cooling of the cement mix, e.g.,hydraulic cement mix, and the like. It will be appreciated thatmodulation may be achieved by human operators who control the necessaryvalves and the like to achieve a desired carbon dioxide exposure and/orother characteristic of the carbonated cement mix, but in generalautomatic control mechanisms are employed. The control may be based onany suitable parameter, such as feedback regarding one or morecharacteristics of the mix operation, timing, which may be apredetermined timing, or a combination thereof.

Control systems and mechanisms can apply to a stationary mixer in aprecast concrete plant or other central mixing facility. Alternatively,it can apply to a ready mix concrete truck that facilitates mixingthrough rotation of its drum. The mix operation can be a dry cast or wetcast operation; for example, the ready mix concrete truck will be a wetcast, while precast may be wet cast or dry cast.

A simple form of control is based on timing alone. Thus, in certainembodiments, the methods include modulating the flow of carbon dioxideto the cement mix, e.g., hydraulic cement mix according to a certaintiming. The timing may be controlled by a controller that is connectedto a cement mix, e.g., hydraulic cement mix apparatus and that senseswhen the apparatus has begun or stopped a stage of operation, and thatmodulates carbon dioxide flow accordingly, e.g., starts or stops flow.Thus in certain embodiments, carbon dioxide flow is begun when one ormore components of a cement mix, e.g., hydraulic cement mix have beendeposited in a mixer, continues for a certain predetermined time at acertain predetermined flow rate, then stops. The stage of operation ofthe cement mix, e.g., hydraulic cement mix apparatus may be determinedby the programming of the controller or of another controller to whichthe controller is operably connected, or it may be determined by one ormore sensors which monitor positions of components of the apparatus,flow, and the like, or a combination thereof.

Typically, however, control systems and mechanisms of the inventioninclude feedback mechanisms where one or more characteristics of thecement mix, e.g., hydraulic cement mixture and/or apparatus or itsenvironment is monitored by one or more sensors, which transmit theinformation to a controller which determines whether one or moreparameters of the mix operation requires modulation and, if so, sendsthe appropriate output to one or more actuators to carry out therequired modulation. The controller may learn from the conditions of onebatch to adjust programming for subsequent batches of similar or thesame mix characteristics to optimize efficiency and desiredcharacteristics of the mix.

In order to achieve a desired efficiency of carbon dioxide uptake in thecement mix, e.g., hydraulic cement mix, to ensure desiredcharacteristics such as flow characteristics, strength, and appearance,and/or to ensure worker safety, various aspects of the mix operation,the mixer, the cement mix, e.g., hydraulic cement mix, and theenvironment of the mixer may be monitored, the information from themonitoring processed, and adjustments made in one or more aspects of themix operation in order to achieve the desired result. Thus, in certainembodiments of the invention, one or more sensors may be used to provideinput to a controller as to various conditions related to the desiredcharacteristics; the controller processes the inputs and compares themto predetermined parameters of operation and, if corrections in theprocess are necessary, the controller then sends output to one or moreactuators in order to bring the system back toward the desiredcondition.

In particular embodiments, the invention provides control systems forcontrolling the carbonation of a cement mix, e.g., hydraulic cement mixin a mixer by use of one or more sensors monitoring one or more ofweight of the cement used in the mix, carbon dioxide concentration ofthe atmosphere inside and/or outside the mixer, temperature of thecement mix, e.g., hydraulic cement mix or a component in contact withthe cement mix, e.g., hydraulic cement mix, rheology of the mix, and/ormoisture content of the mix, where the one or more sensors send input toa controller which processes the information received from the one ormore sensors by comparing the input to one or more predeterminedparameters and, if necessary, sends output to one or more actuators toadjust carbon dioxide flow rate, water addition, or admixture addition,or to perform other functions such as to sound an alarm if carbondioxide levels exceed safe levels. In addition, certain operations, suchas cooling of the cement mix, e.g., hydraulic cement mix, may beperformed after the mixing is complete. The controller can learn fromone batch to adjust conditions for a subsequent batch of the same orsimilar composition. Further levels of control may be used, such as acentral controller that receives information from a plurality of mixoperations in a plurality of locations regarding one or more aspects ofeach operation, and processes the information received from all mixoperations to improve performance at the various operations; thus, largeamounts of information can be used to improve performance at a varietyof sites.

In the mixing operation, components of the cement mix, e.g., hydrauliccement mix, e.g., cement, aggregate, and water, are added to the mixer,and mixing commences. In some cases some components, such as aggregate,may have a sufficient water content, e.g., from exposure to wet weatherconditions, that additional water is not added before mixing commences.In some cases, as described elsewhere herein, water or other componentsmay be added in a staged manner. At some point before, during, or afterthe process of addition of components or mixing, carbon dioxide flow isinitiated from a source of carbon dioxide to the mixer. In some cases,part or all of the carbon dioxide will be included in the mix water. Insome cases, the carbon dioxide flow will be gaseous; in other cases, thecarbon dioxide flow comprises a mixture of gaseous and solid carbondioxide. Additional components, such as admixtures, may be added to thecement mix, e.g., hydraulic cement mix as well at any point in theoperation. The carbon dioxide is subsumed into the mixing cement mix,e.g., hydraulic cement mix and begins reaction with the mix components;any carbon dioxide that is not taken up by the cement mix, e.g.,hydraulic cement mix fills the head space of the mix container. Sincetypical mixers are not airtight, if the rate of carbon dioxide flow tothe mixer exceeds the rate of uptake into the cement mix, e.g.,hydraulic cement mix, at some point the head space in the mixer will befull of carbon dioxide and excess carbon dioxide will exit the mixerfrom one or more leak points. Thus, the carbon dioxide content of theatmosphere inside the mixer or, more preferably, outside the mixer,e.g., at one or more leak points, may be monitored to provide anindication that the rate of carbon dioxide addition is exceeding therate of carbon dioxide uptake. In addition, carbon dioxide levels inareas where workers are likely to be may also be monitored as a safetyprecaution. The reaction of carbon dioxide with the hydraulic cement isexothermic, thus the temperature of the cement mix, e.g., hydrauliccement mix rises; the rate of temperature rise is proportional to therate of carbon dioxide uptake and the overall temperature rise isproportional to total carbon dioxide uptake for a given mix design.Thus, the temperature of the cement mix, e.g., hydraulic cement mix, orthe temperature of one or more portions of the mix container or otherequipment that are in contact with the mix, may be monitored as anindication of rate and extent of carbon dioxide uptake into the cementmix, e.g., hydraulic cement mix. Carbonation of components of the cementmix, e.g., hydraulic cement mix may produce a change in the flowcharacteristics, i.e., rheology, of the cement mix, e.g., hydrauliccement mix, which can be undesirable in certain applications, e.g., inwet cast applications such as in a ready mix truck. Thus, the rheologyof the cement mix, e.g., hydraulic cement mix may be monitored. Inaddition, carbonation may affect the moisture characteristics of thecement mix, e.g., hydraulic cement mix, which may lead to undesirablecharacteristics, and moisture content of the mix may be monitored aswell.

The invention also provides a network of mix systems with one or moresensors and, optionally, controllers, that includes a plurality of mixsystems, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, or more than 10 mix systemswith one or more sensors and, optionally, controllers, each of whichtransmits data from their respective locations and mix conditions to acentral controller, which learns from the overall data from all the mixsystems and provides updated and modified mix instructions to thevarious mix systems in the network based on this information. In thisway the operation of each individual mix system within the network canbe optimized based on information from all the other mix systems in thenetwork. Thus, timing and extent of carbon dioxide delivery, admixturetype and amount, water amount and timing and delivery, and other factorsmay be optimized for one site before it has even begun its first batch,based on historical information from other sites, and all sites mayundergo continual improvement in optimization as the sensors, and,optionally, controllers in the network continually gain more informationand feed it to the central controller.

Thus, in certain embodiments the methods and/or apparatus of theinvention may include feedback mechanisms by which one or morecharacteristics of the the type of mixer apparatus, cement mix, e.g.,hydraulic cement mix, a gas mixture in contact with the cement mix,e.g., hydraulic cement mix and inside or outside of the mixer, acomponent of the cement mix, e.g., hydraulic cement mix productionapparatus, a component exposed to the cement mix, e.g., hydraulic cementmix, or the environment of the mixer, is monitored and the informationis used to modulate the exposure of the cement mix, e.g., hydrauliccement mix to carbon dioxide, one or more admixtures, water, or othercomponents, in the current mix and/or in subsequent mixes.Characteristics such as carbon dioxide content monitored inside and/oroutside the mixer, and/or temperature of the mix monitored inside themixer or outside of the mixer, of a component in contact with the cementmix, e.g., hydraulic cement mix, e.g., a surface of the mixer such asthe outer surface of the mixer, and/or position or state of operation ofa component of the cement mix, e.g., hydraulic cement mix productionapparatus, may be used to determine when to modulate carbon dioxideaddition, e.g., to start or to stop or slow carbon dioxide addition.Certain safety monitoring may also be done, e.g., monitoring of areasoutside the mixer for carbon dioxide levels to ensure worker safety.

In general, feedback systems include one or more sensors for monitoringone or more characteristics and sending input to a controller, whichreceives the input from the sensors, processes it, and, if necessary,sends output, based on the processing, to one or more actuators that isconfigured to alter some aspect of the exposure of the cement mix, e.g.,hydraulic cement mix to carbon dioxide, water, admixture, or some otheraspect of the operation of the cement mix, e.g., hydraulic cement mixapparatus. In the simplest case, a human operator may manually begincarbon dioxide exposure by adjusting a valve, then may monitor acharacteristic by using one or more sensors, e.g., a handheldtemperature sensor that is pointed at the drum of a readymix truck,and/or a simple timer, and halt the supply of carbon dioxide gas when acertain temperature or a certain time is reached. However, in generalautomatic feedback mechanisms are used.

Sensors

Suitable sensors for use in control systems of the invention includetemperature sensors, carbon dioxide sensors, rheology sensors, weightsensors (e.g., for monitoring the exact weight of cement used in aparticular batch), moisture sensors, other gas sensors such as oxygensensors, pH sensors, and other sensors for monitoring one or morecharacteristics of a gas mixture in contact with the cement mix, e.g.,hydraulic cement mix, a component of the cement mix, e.g., hydrauliccement mix production apparatus, a component exposed to the cement mix,e.g., hydraulic cement mix, or some other aspect of the mix operation.Sensors also include sensors that monitor a component of the cement mix,e.g., hydraulic cement mix apparatus, such as sensors that detect whenmixing has begun, when components of a cement mix, e.g., hydrauliccement mix have been added to a mixer, mass flow sensors, flow rate orpressure meter in the conduit, or other suitable sensors.

Cement Weight Scale Sensor

A cement weight scale sensor can be used to transmit information to thecontroller concerning the mass of cement that will be in a given mixturein the mixer. Since the CO₂ is dosed in proportion to the mass ofcement, this weight is important for determining the correct dose toachieve the desired outcomes. The cement mass is also used to scale thesize of a given batch, given that a mixture could vary in relation to adefault size such as a full batch (100%) or a quarter batch (25%), orany other batch size. In some cases the batch could even exceed 100%.This batch size can also be used to determine the head (free) space inthe mixer so that it can be rapidly filled with CO₂ without creating anoverpressure by delivering more than the headspace will allow. Once thehead space is full, the flow rate can be reduced to match the uptakerate of the cement.

Carbon Dioxide Sensors

One or more CO₂ sensors may be used to minimize waste, i.e., to increasethe efficiency of carbon dioxide uptake, and/or to ensure worker safety.The CO₂ sensors work by measuring the CO₂ content of the air around theoutside of the mixer and/or inside the mixer. Alternatively, oradditionally, one or more sensors may be located inside the mixer andsense the carbon dioxide content of the gas in the mixer and send asignal to a controller. The sensors may be any sensor capable ofmonitoring the concentration of carbon dioxide in a gas and transmittinga signal to the controller based on the concentration, and may belocated in any convenient location or locations inside or outside themixer; if inside, preferably in a location such that the sensor is notsubject to fouling by the cement mix, e.g., hydraulic cement mix as itis being mixed or poured. In addition to, or instead of, carbon dioxidesensors inside the mixer, one or more such sensors may be locatedoutside the mixer to sense the carbon dioxide content of overflow gasescaping the mixer and send a signal to a controller. In either case, acertain range or ranges, or a cutoff value, for carbon dioxide contentmay be set, and after the carbon dioxide content of the mixer and/oroverflow gas reaches the desired range, or goes above the desiredthreshold, carbon dioxide delivery, or some other aspect of the cementmix, e.g., hydraulic cement mix apparatus, may be modulated by a signalor signals from the controller to an actuator or actuators. For example,in certain embodiments a carbon dioxide sensor may be located outsidethe mixer and when carbon dioxide content of the overflow gas reaches acertain threshold, such as a carbon dioxide concentration that indicatesthat the gas mixture in contact with the cement mix, e.g., hydrauliccement mix is saturated with carbon dioxide, carbon dioxide delivery tothe cement mix, e.g., hydraulic cement mix, e.g., inside the mixer ishalted or slowed by closing a valve, partially or completely, in theconduit from the carbon dioxide source to the mixer.

In particular, for minimizing waste, one or more sensors can be placedin the areas where leaks are most likely to occur (e.g., around doors,etc.). The sensor or sensors may be positioned so that leaking carbondioxide is most likely to pass in their vicinity, e.g., since carbondioxide is more dense than air, positioning below a likely leak point ismore desirable than positioning above a likely leak point. When the gasis delivered at a rate much greater than capacity of the cement toabsorb the CO₂ it is more likely to spill out of the mixer at a leakpoint and be detected by a gas sensor. Leaks would be a normallyoccurring event when there is too much gas delivered to the mixer giventhat the mixer is not completely gas tight according to the nature ofthe machine. A CO₂ leak would occur when the CO₂ has been delivered tooquickly. Given that CO₂ is heavier than air there would be, in general,a certain amount of CO₂ that can be delivered to the mixer wherein theincoming CO₂ gas would displace air that initial was sitting in themixer. Once the air has been displaced an delivery of additional gaswould displace previously delivered carbon dioxide or otherwise beimmediately spilled from the mixer. Sensors that feed into a dosinglogic system would preferably be placed in locations immediately besidethe mixer leak points. If the one or more sensors read that the CO₂content in the vicinity exceeds a preset threshold level (e.g. a definedbaseline), the system will adjust the CO₂ flow rate and/or deliverytime, e.g., to decrease or eliminate additional overspill in the presentbatch or to eliminate the overspill in a future mixing cycle. The logiccan co-ordinate a filling rate of the mixer space that is proportionalto the uptake rate of CO₂ by the cement.

For worker safety, if a carbon dioxide delivery causes the carbondioxide concentration in areas around the mixer normally accessed byworkers to exceed a maximum value (such as indicated by OSHA), thecontroller can signal for a system shut down wherein all the valves canbe closed and, typically, an alarm can be sounded as a safety measure.Sensors that feed into a safety system can be placed at variousdistances from the mixer depending on the proximity requirements forworkers to the mixer.

Temperature Sensors

One or more sensors may be used to monitor the temperature of the mixinside or outside of the mixer and/or of a component in contact with thecement mix, e.g., hydraulic cement mix and/or of the mixer, which isindicative of carbonation and/or other reactions due to the addition ofthe carbon dioxide, and carbon dioxide addition modulated based on thistemperature or temperatures monitored by the sensor(s). One or moretemperature sensors may be located to monitor the temperature of thecement mix, e.g., hydraulic cement mix, for example, within the mixer,or at a site distal to the mixer such as a holding site or transportsite for the cement mix, e.g., hydraulic cement mix. Such a site may be,e.g., a feedbox for a pre-cast operation, or a belt or other transportmode, or a wheelbarrow or other site for transporting or storingconcrete from a ready-mix truck. One or more temperature sensors may belocated to monitor the temperature of a component that is in contactwith the cement mix, e.g., hydraulic cement mix, e.g., the drum of themixer. Any suitable temperature sensor may be used. For example, ainfrared temperature sensor, such as a mounted or handheld sensor, maybe used to monitor the temperature of the drum of a ready-mix truck towhich carbon dioxide is added, and when a certain temperature is reachedor range of temperatures achieved, the addition of the carbon dioxideinside the drum may be modulated.

The temperature or range of temperatures at which the carbon dioxideexposure is modulated may be a predetermined temperature or range, basedon a temperature known to be associated with one or more undesirablecharacteristics, e.g., reduced strength, workability loss, poorcompactability performance, hardening in the mixer, etc. In some casesit may be an absolute temperature or range. More preferably, it is atemperature or range that is determined in reference to an initialtemperature, such as an initial temperature of the cement mix, e.g.,hydraulic cement mix or a component in contact with the mix beforeaddition of carbon dioxide. In certain embodiments, the temperature orrange is at least 10, 15, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 35,40, 45, or 50° C. above the initial temperature, or 10-50, 10-40, 10-30°C. above the initial temperature, and with that range a threshold may beset, which may vary from batch to batch depending on the desiredcarbonation of the concrete mix or other characteristics. In certaincases, e.g., where warm starting materials are used, the temperature iskept unchanged from the starting temperature, or kept within 0-5° C. ofthe starting temperature. In some case, an absolute maximum temperatureis set and the control system is configured to keep the mix below themaximum temperature. The sensor can also be used to monitor rate oftemperature rise and the controller can adjust the flow rate and/ordelivery time if the rate is too high or too low. Test data indicatesthat, for a constant flow, the carbon uptake is proportional totemperature increase detected immediately after carbonation for a givenmix. An in-situ temperature measurement may be used to model thereal-time total carbon dioxide uptake of the cement mix, e.g., hydrauliccement mix with respect to previously collected calibration data.

Rheology Sensors

In an operation in which flowability of the cement mix is important,e.g., a wet cast operation, one or more rheology sensors may be used. Arheometer can be mounted inside the mixer to measure the workability ofthe cement mix, e.g., hydraulic cement mix. CO₂ can reduce theworkability of the fresh cement mix, e.g., hydraulic cement mix, and therheometer can be used to monitor the workability loss. At a certainpreset minimum threshold of workability, one or more actions may betriggered, such as modulation of the rate of CO₂ flow to the mixer,addition of admixture, and/or addition of additional water, to restoreworkability to a desired level. A rheometer can also monitor theworkability of concrete in a ready mix concrete truck while it is intransit and adjust CO₂/admixture doses on subsequent mixtures producedat the batching plant, or even adjust an admixture dose delivered in thedrum truck itself

Moisture Sensors

One or more moisture sensors may be used. The moisture sensor is used tomonitor the moisture in the cement mix, e.g., hydraulic cement mixduring the mixing cycle. As CO₂ is taken up by the cement mix, e.g.,hydraulic cement mix, the apparent moisture can be reduced and result ina drier looking product. Therefore the mix moisture may need to beincreased to maintain the desired product appearance. If the moisturereaches a minimum threshold value, the CO₂ can be modulated, e.g.,reduced or shut off so the mix is not released in an unacceptably drycondition. The sensor also monitors the moisture decrease with respectto CO₂ uptake and can adjust the flow rate and/or delivery time if therate becomes too high or too low. The moisture sensor can also triggerthe addition of supplemental mix water at any point in the mixingprocess. In addition, one or more moisture sensors may be used todetermine the moisture content of one or more components of the cementmix, e.g., hydraulic cement mix before the components are mixed; forexample, a moisture sensor may be used to determine the moisture contentof aggregate, which may be exposed to weather conditions leading towater pickup. In the case of an operation where carbon dioxide is addedvia mix water as well as by gas or liquid, such information may be usedto adjust the relative amount of carbon dioxide added via gas or liquid,to compensate for the fact that less mix water will be used due to themoisture content of the aggregate.

Other Sensors

One or more sensors may monitor conditions of the cement mix, e.g.,hydraulic cement mix apparatus and send a signal to a controller. Forexample, one or more sensors may monitor when all desired components ofthe cement mix, e.g., hydraulic cement mix are in the mixer and mixing,and the controller may send a signal to an actuator, such as acontrollable valve, to begin flow of carbon dioxide. The carbon dioxideflow may continue for a predetermined time, or may be modulatedaccording to further feedback, such as described above.

Other conditions may be monitored, as well, such as pressure conditionsin one or more lines; for example, in a system where liquid carbondioxide is delivered to the mixer, sensors may be employed to controldry ice formation between the nozzle and solenoid as well as to confirmpre-solenoid pressure is maintained to ensure the line remains liquid.

Any combination of one or more sensors inside or outside the mixer,and/or inside or outside the mix, may be used to monitor cement binderweight, cement binder location, carbon dioxide content, temperature,rheology, moisture content, pH, other characteristics, or a combinationthereof, and feedback loops to modulate the addition of carbon dioxidebased on the information provided by these sensors may be used; suchloops may include automatic or manual adjustments, or both. In certainembodiments, sensors monitor the cement binder addition time and/or dustcollector system operation time, as in some mixers a fan is run afterthe powders go in to prevent excessive dust, and these should be turnedoff so that added carbon dioxide is not removed during this time.

Thus, in certain embodiments the invention provides a method orapparatus for producing carbonated cement mix, e.g., hydraulic cementmix that includes a control system that includes at least one sensorselected from the group consisting of a carbon dioxide sensor, atemperature sensor, a rheology sensor, and a moisture sensor. In certainembodiments the invention provides a method or apparatus for producingcarbonated cement mix, e.g., hydraulic cement mix that includes acontrol system that includes at least two sensors selected from thegroup consisting of a carbon dioxide sensor, a temperature sensor, arheology sensor, and a moisture sensor. In certain embodiments theinvention provides a method or apparatus for producing carbonated cementmix, e.g., hydraulic cement mix that includes a control system thatincludes at least three sensors selected from the group consisting of acarbon dioxide sensor, a temperature sensor, a rheology sensor, and amoisture sensor. In certain embodiments the invention provides a methodor apparatus for producing carbonated cement mix, e.g., hydraulic cementmix that includes a control system that includes a carbon dioxidesensor, a temperature sensor, a rheology sensor, and a moisture sensor.The methods and apparatus can further include one or more actuators foradjusting some aspect of the mix operation, for example carbon dioxideflow to the mixer, or admixture flow to the mixer, and a controller thatreceives signals from the sensor or sensors, processes them to determineif modulation of the mix operation is required, and, if so, transmits asignal to an actuator or actuators to carry out the modulation.

Actuators

The actuator or actuators may be, e.g., one or more valves, such assolenoid valve, in one or more conduits supplying a component, such ascarbon dioxide, to the mixer, as described elsewhere herein. An actuatorfor CO₂ delivery can be, e.g., a delivery manifold with, e.g. gastemperature sensor, gas pressure gauge, modulating control valve,open/close solenoid and orifice plate assembly. These components can allbe combined in a singular unit, i.e. a flow controller. In certainembodiments, in addition to or alternatively to, a gas delivery system,one or more actuators for controlling delivery of carbonated mix water,as described herein, may be used. Such actuators may include, e.g.,actuators to control charging mix water with carbon dioxide and/oractuators to control delivery of carbon dioxide-charged water to themixer. Similarly, an actuator controlling water delivery to the mix maybe under the control of the controller, as may be an actuatorcontrolling delivery of one or more admixtures to the mix. In addition,an actuator may include a relay switch attached to dust collector powersource to shut off mixer dust collector during CO₂ delivery (ifnecessary). In general, the modulation of the carbon dioxide exposurewill be an increase or decrease in exposure, such as a decrease in flowrate of carbon dioxide gas to the mixer. In certain embodiments, themodulation is halting the flow of carbon dioxide gas to the mixer.

Thus, in certain embodiments the invention provides a method orapparatus for producing carbonated cement mix, e.g., hydraulic cementmix that includes a control system that includes at least one actuatorfor controlling at least one action selected from the group consistingof a carbon dioxide flow to the mixer, water flow to the mixer, andadmixture flow to the mixer. In certain embodiments the inventionprovides a method or apparatus for producing carbonated cement mix,e.g., hydraulic cement mix that includes a control system that includesat least two actuators for controlling at least two actions selectedfrom the group consisting of a carbon dioxide flow to the mixer, waterflow to the mixer, and admixture flow to the mixer. In certainembodiments the invention provides a method or apparatus for producingcarbonated cement mix, e.g., hydraulic cement mix that includes acontrol system that includes an actuator for controlling carbon dioxideflow to the mixer, an actuator for controlling water flow to the mixer,and an actuator for controlling admixture flow to the mixer.

Other actuators, such as actuators that control one or more aspects ofhydraulic cement production, such as timing of mixing, delivery ofcooling input such as ice or liquid nitrogen, activation of an alarm,and the like, may also be used as appropriate.

Controller

The control systems used in methods and apparatus of the inventioninclude a controller that receives inputs from the one or more sensors,processes them by comparing them to preset values for achieving thedesired result, and, as necessary, sends outputs to the one or moreactuators to move the system toward the desired result.

The controller may be, e.g., an electronic circuit or a programmablelogic controller, located either on-site with the mixer or off-site,e.g., as part of a computer network. For example, the controller may bea Programmable Logic Controller (PLC) with a Human Machine Interface(HMI), for example a touch screen and onboard telemetry computer. Thecontroller can be integrated into the overall mixer controller or it canbe a separate unit that receives inputs from the mixer controller asappropriate.

An exemplary set of operations for a controller in response to inputsfrom various sensors and giving outputs to various actuators isillustrated below.

The system can include the following components: 1) Programmable LogicController (PLC) with attached Human Machine Interface (HMI), forexample a touch screen and onboard telemetry computer. 2) Gas deliverymanifold with, e.g., gas temperature sensor, gas pressure gauge,modulating control valve, open/close solenoid and orifice plateassembly. These components can all be combined in a singular unit, i.e.a flow controller. 3) Cement weight scale feeding into a concrete mixerto measure quantity of cement used in a batch. This quantity is usedlogically to determine the CO₂ dose based on cement content (furtherinformation below). 4) Proximity switch to trigger the delivery of CO₂into the mixer 5) Relay switch attached to dust collector power sourceto shut off mixer dust collector during CO₂ delivery (if necessary). 6)One or more CO₂ sensors positioned around the mixer used to monitorcarbon dioxide gas concentration outside the mixer. The data can be usedlogically to minimize wastage by controlling flow or monitor safety(further information below). 7) Concrete temperature sensor in or onmixer used to monitor the concrete temperature during the carbonationtreatment. The data can be used logically to control the CO₂ dose aswell as the flow rate (further information below). 8) Moisture sensorused to monitor concrete moisture in the mixer. This information can beused to logically control the CO₂ dose (further information below). 9)Concrete rheology sensor to monitor the consistency of the concrete.Information about the workability of the concrete can logically be usedto signal admixture delivery or process end points. Not all of thesecomponents need be present, depending on the needs of the mix operation.For example, in a dry cast operation, a rheology sensor may not be used.

The steps of operation of the system are as follows:

1. A PLC is programmed, for example, through the HMI, to apply carbondioxide treatment to a first batch. Process threshold settings foraspects such as CO₂ concentration in the air at a leak point and/or at aworker area, concrete temperature and/or rate of temperature change,concrete moisture and/or rate of moisture change, concrete rheology canbe input at this time.

2. Batching starts by a signal from the mixing controller to the mixer.This follows logically after the previous step. The mixer controllersoftware can communicate batch information to the PLC.

3. Materials are added to mixer (e.g. aggregates). This followslogically after the previous step as part of normal practice.

4. The cement is weighed. This follows logically after the previous stepas part of normal practice. A cement mass (weight) sensor determinesmass (weight) of cement used in the batch and feeds information to thePLC

5. The PLC makes a calculation to determine the required gas flow. Thisfollows logically from an earlier step. The PLC calculates the amount ofgas required for delivery to the current mix based upon a percentagedosage rate of gas mass to cement mass. The PLC calculation may refer toa predetermined set point. It may alternatively, or in addition, callupon historical data of previous combinations of mix size, mix type andCO₂ dosage rate, either from the mix site at which the current batch isbeing mixed, or from other mix sites, or a combination thereof. It canuse information (either input or detected) about the batch size, cementmass, mix type and mixer volume. For example, it can use informationabout cement type or origin to determine whether, which, and/or how muchadmixture should be employed. The PLC can accept information requiredfor calculations from sources including user input into the HMI,communication with the mixer controller software, and the cement masssensor. The PLC calculations will depend upon acquiring all of therequired data which can come from, e.g., the HMI in step 1, mixcontroller software in step 2, and/or the cement mass sensor in step 4.

6. Cement is dropped into the mixer. This follows logically after theprevious step. The time that cement enters the mixer is detected. Aproximity sensor can detect the cement deposit in the mixer through aphysical movement (e.g. the opening of a door or gate). Alternatively,the cement addition time can be supplied synchronously from the mixercontroller software. The time that the cement is placed into mixer istransmitted to the PLC.

7. The PLC starts the gas delivery. This can be concurrent with theprevious step, at some predetermined time after the previous step, oreven before the previous step, if it is desired to replace some or allof the air in the mixer with CO₂ prior to deposition of the cement. ThePLC can send a signal to the mixer dust collector to be turned off forall or part of the CO₂ delivery or otherwise coordinated with someaspect of the gas delivery. The PLC sends signal to the solenoid in theCO₂ delivery system to open either in coordination with the cementinsertion or at some time before or after the insertion.

8. The PLC surveys the sensors for any process conditions that signalthe CO₂ delivery is to change/end according to preset conditions or forother measurable aspects. This follows logically after the previousstep. A) Temperature sensor—the concrete temperature exceeds a thresholdvalue or rate that can be set for correlation to a maximum allowabletemperature rise or a target temperature rise. B) CO₂ leak sensors—theCO₂ sensors at the significant leak points of the mixer have detected aCO₂ content that exceeds a preset threshold or a relative value above abaseline measurement. C) CO₂ safety sensors—the CO₂ sensors monitoringthe CO₂ content of the air in the general vicinity of the mixer havereached a threshold value. There can also be an oxygen sensor measuringthe oxygen content of the air. These sensors are located in areasaccessed by workers around the machine as opposed to leaks immediatelyfrom the mixer. D) Moisture sensor—the moisture content of the concretehas reached an absolute threshold with respect to a set point orotherwise has passed a relative measure with respect to the batch athand. For example, a condition might acknowledge that the moisturecontent of the concrete inherently varies from batch to batch but wouldsearch for a decline in moisture content of, e.g., 0.5% with respect tothe measurement expected if no CO₂ had been applied or the initialmeasurement, etc. E) Rheology—(relevant to wet mix) the workability ofthe concrete is measured and found to reach a threshold level. F) Timeron PLC—PLC may have a predefined maximum delivery time that may signal astop condition in the event no other sensors have triggered a stop.

9. A gas flow modification condition is detected. The PLC receives asignal from a sensor and modifies the gas delivery in response. Followslogically from previous step. A) Any sensor may suggest the gas inputflow is modified (e.g., reduced) as a threshold value is neared ratherthan simply attained or crossed. B) Temperature Sensor—if the sensordetects an increase in the temperature of the concrete that is greaterthan expected then a signal can be sent by the PLC to reduce the rate ofinput of carbon dioxide. Conversely, if the rate of temperature increaseis lower than expected then the PLC can increase the rate input ofcarbon dioxide. In addition or alternatively, if a certain thresholdtemperature is reached, carbon dioxide delivery may be halted. C) CO₂leak sensors—if the sensors detect an increase in CO₂ concentration atthe mixer leak points a signal can be sent to the PLC, which reduces theinput of carbon dioxide. For example, the leaking can be an indicationthat the head space of the mixer has been filled with CO₂ and anyfurther addition will result in leaks or overspill. The CO₂ input may bereduced to a rate that is in proportion to the projected absorption rateof the carbon dioxide into the cement. Thereby any gas that is absorbedinto the concrete is in turn replaced with new gaseous CO₂ to maintainan overall amount of gas in the mixer. D) Rheology sensor—if the sensordetects a decrease, e.g., a rapid decrease in the workability of theconcrete, a signal can be sent by the PLC to reduce carbon dioxideinput. Conversely, if the workability loss is less than expected, thePLC can increase the carbon dioxide input. Other outputs from the PLCmay cause addition of admixture, water, or both to the mix.

10. A gas delivery stop condition achieved, PLC receives signal to stopgas delivery. Follows logically from previous step. Solenoid is closed.Gas delivery ends.

11. After the CO₂ delivery is complete the sensors may send signals tothe controller that call for supplemental inputs to the mixer. Followslogically from previous step. A) Temperature sensor can detect atemperature rise that calls for the concrete temperature to be reducedthrough the addition of a cooling input such as ice or liquid nitrogen.B) Temperature sensor detects that the target CO₂ uptake of the concretehas been achieved which may prompt the addition of an appropriateadmixture. C) Moisture sensor reading causes PLC to signal foradditional mix water or other remedial measure such as an admixture. D)Rheology sensor input to PLC causes output for additional mix wateraddition, or an admixture addition, or both, to facilitate a workabilityincrease or other remedial measure.

12. Batching and mixing is complete. Concrete is released to theremainder of the production cycle. Follows logically from previous step.

13. The PLC can perform calculations to learn for subsequentbatches—particularly for the next time that same or similar combinationof mix design and CO₂ dosage is used. Otherwise settings can bepredicted for other CO₂ dosages to apply to that same mix design, or forsmaller batches of that mix design with the same CO₂ dosage, etc. Thiscan be concurrent with previous step. A) The data from CO₂ leak sensorscan dictate that, for a future mix, the flow rate should be reduced ifthere were excessive leaks (too much gas is supplied) or increasedbecause there are no leaks at all (not enough gas has been supplied) inthe present mix. The PLC will make note of the updated or recalculatedgas flow setting for future use. B) Temperature data can inform futurecooling treatment usage. The PLC will make note of the temperatureresponse in the wake of the applied temperature adjustment foradjustment of the cooling treatment in future batches. For example thefuture cooling treatment can be greater or lower if the current coolingtreatment was found to be inadequate. C) Temperature data can informfuture kinetic assessments of temperature rise vs time for a givencombination of mix design and gas delivery condition. D) The moisturesensor data can inform future mix water adjustment required either to beincluded as part of the initial mix water or as late addition mix water.In the first case the total water addition might be approachedincrementally whereas later mixes can use the end point determined inthe first mix as a target setting. E) Rheological information can informfuture admix usage. The PLC can correlate a quantified dose of admixwith the response in workability metric. The proportion of admix toaspects such as, but not limited to, cement content, absorbed carbondioxide (either measured directly after the fact or approximated bytemperature increase) workability improvement can be recorded andrecursively recalculated as additional data is acquired therebyimproving the admix dosing logic. Further information regardingcharacteristics of the batch, such as flowability or strength at one ormore time points, water absorption, and the like, may also be input.

14. Telemetry data can be logged and distributed by the PLC to a remotedata storage. This can be concurrent with the end of gas delivery (step10) or follow from later steps if additional information acquired afterthe end of delivery is part of the transmitted information.

Exemplary mixers and control systems are illustrated in FIGS. 1, 2, and3. FIG. 1 shows a stationary planetary mixer, e.g., for use in a precastoperation. The cement scale 1 includes a mass sensor that sends dataregarding the mass of cement dispensed from the cement silo 2 to thecontroller 10. Proximity sensor 3 senses when cement is released to themixer and sends a signal to the controller; alternatively, the mixcontroller (not shown) can send a signal to the controller 10 when thecement is released. CO₂ delivery may commence upon release of thecement; alternatively, CO₂ delivery may commence before or afterrelease. CO₂ sensors 8 and 9 are located at leak areas outside the mixerand send signals regarding atmospheric CO₂ content to the controller 10.In addition, temperature sensor 6 sends signals regarding thetemperature of the concrete mix to the controller 10. Additionalsensors, such as moisture and rheology sensors, or additional CO₂sensors in worker areas in the vicinity of the mixer may be used (notshown) and send additional signals to the controller. Controller 10processes the signals and sends output to an actuator 11 for controllingdelivery of CO₂ from a CO₂ supply 13 via a conduit to the CO₂ gas mixerinlet 7, where it enters the mixer headspace 4 and contacts the mixingconcrete 5. For example, in a basic case, the controller 10 may send asignal to the actuator 11 to open a valve for delivery of CO₂ uponreceiving input from the proximity sensor 3 indicating that cement hasbeen delivered to the mixer, and send a signal to the actuator 11 toclose the valve upon receiving input from one or more of the CO₂ sensors8 and 9 or the temperature sensor 6 indicating that the desired deliveryof CO₂ to the mixer, or uptake of CO₂ into the concrete has beenachieved. The controller may send output to additional actuators such asan actuator for controlling water addition or an actuator controllingadmixture addition (not shown). An optional telemetry system 12 may beused to transmit information regarding the batch to a central locationto be used, e.g., to store data for use in future batches and/or to usefor modification of the same or similar mixes in other locations.

FIGS. 2 and 3 show a mobile cement mixer, in this case, a ready mixtruck. FIG. 2 shows a ready mix truck 1 with a detachable carbon dioxidedelivery system. Carbon dioxide is supplied from a carbon dioxide supply8 via a conduit that is attachable to a conduit on the truck 2 at ajunction 4. Controller 6 controls the supply of carbon dioxide to thedrum of the truck 2 via an actuator 5. Sensors, such as CO₂ sensors maybe located at leak areas outside and/or inside the drum 2 and sendsignals regarding atmospheric CO₂ content to the controller 6. Inaddition, one or more temperature sensors may sends signals regardingthe temperature of the concrete mix to the controller 6. Additionalsensors, such as moisture and rheology sensors, or additional CO₂sensors in worker areas in the vicinity of the mixer may be used (notshown) and send additional signals to the controller. The controllerssends a signal to the actuator (e.g., valve) 5 to control addition ofcarbon dioxide to the drum 2. Additional actuators may be controlled bythe controller, such as to control addition of an admixture to the drum2. An optional telemetry system 7 may be used to transmit informationregarding the batch to a central location to be used, e.g., to storedata for use in future batches and/or to use for modification of thesame or similar mixes in other locations. FIG. 3 shows a ready mix truckwith attached carbon dioxide delivery system that travels with the truck1. This can be useful to, e.g., optimize exposure of the cement mix tocarbon dioxide. Carbon dioxide is supplied from a carbon dioxide supply7 via a conduit 3 that is attachable the truck and delivers carbondioxide to the drum of the truck 2. Controller 5 controls the supply ofcarbon dioxide to the drum of the truck 2 via an actuator 4. Sensors,such as CO₂ sensors may be located at leak areas outside and/or insidethe drum 2 and send signals regarding atmospheric CO₂ content to thecontroller 5. In addition, one or more temperature sensors may sendssignals regarding the temperature of the concrete mix to the controller5. Additional sensors, such as moisture and rheology sensors, oradditional CO₂ sensors in worker areas in the vicinity of the mixer maybe used (not shown) and send additional signals to the controller. Thecontrollers sends a signal to the actuator (e.g., valve) 4 to controladdition of carbon dioxide to the drum 2. Additional actuators may becontrolled by the controller, such as to control addition of anadmixture to the drum 2. An optional telemetry system 6 may be used totransmit information regarding the batch to a central location to beused, e.g., to store data for use in future batches and/or to use formodification of the same or similar mixes in other locations. In certainembodiment the controller 5 is located remote from the truck andreceives the signals from the telemetry system, and transmits signalswhich are received and acted upon by the actuator 4.

D. Mixers

The mixer in which the carbon dioxide is contacted with the cement mix,e.g., hydraulic cement mix during mixing may be any suitable mixer. Themixer may be relatively fixed in location or it may provide both mixingand transport to a different location from the mixing location.

In certain embodiments, the mixer is fixed or relatively fixed inlocation. Thus, for example, in certain embodiments the mixer is part ofa pre-casting apparatus. For example, the mixer may be configured formixing concrete before introducing the concrete into a mold to produce aprecast concrete product. In certain embodiments, the mixer isconfigured to mix concrete before introducing the concrete into a mold,and the addition of carbon dioxide to the concrete mix, the componentsof the concrete mix, and, optionally, other ingredients such as one ormore admixtures, are adjusted so that a desired level of flow of theconcrete mix, generally very low or no flow, is combined with a desiredlevel of compactability so that the concrete may be compacted within acertain range of parameters during and after delivery to a mold, and sothat the final product possesses a desired hardening time, strength,shrinkage, and other characteristics as desired. For example, a gas tubeto deliver carbon dioxide into the mixer may be placed with the gas linepositioned in such a way that it does not interfere with the normalmixer operation. Gas is delivered in proportion to the amount of cement,for example in the range 0.5% to 2.5%, or any other suitable range asdescribed herein. The gas delivery can be confined to the normal mixingtime. In certain embodiments gas delivery may be triggered by a gate forthe cement addition pipe. When the gate closes (signalling completion ofcement addition) a magnetic proximity sensor detects the closed stateand triggers the start of the carbon dioxide flow.

In certain embodiments in which the mixer is a fixed mixer, for examplein a dry cast or wet cast pre-casting operation, the mixer is configuredto mix concrete and to deliver it to a holding component, e.g., ahopper, which further delivers the concrete to a mold, optionally via afeedbox. Additional carbon dioxide can be added to the cement mix, e.g.,hydraulic cement mix at the hopper and/or feedbox, if desired. See U.S.patent application Ser. No. 13/660,447 incorporated herein by referencein its entirety. In certain embodiments, no further carbon dioxide isadded to the mix (apart from carbon dioxide in the atmosphere) after theconcrete exits the mixer.

The addition of carbon dioxide may affect the compactability and thusthe strength of the final object, e.g., precast object. In the case of awet cast operation, flowability is also a consideration. Thus, incertain embodiments, the addition of carbon dioxide to the concrete mix,the components of the concrete mix, and, optionally, other ingredientssuch as one or more admixtures, are adjusted so that a desired level ofcompactability (strength) and/or flowability of the cement mix, e.g.,hydraulic cement mix, e.g., concrete, is achieved, generally a level ofcompactability (strength) and/or flowability similar to the level thatwould be present without the addition of the carbon dioxide, so that thefinal product after the concrete is poured into the mold and compactedat possesses a desired strength, such as a desired 1-, 7-, 28 and/or56-day strength, and/or so that the flowability is at a desired value.In the case of the pre-cast mixer, the addition of carbon dioxide,components of the concrete mix, and/or additional components such as oneor more admixtures, may be adjusted so that compactability and/or 1-,7-, 28 and/or 56-day strength of the final concrete mix is within 50,40, 30, 20, 10, 8, 5, 4, 3, 2, 1, 0.5, or 0.1% of the value or valuesthat would be achieved without the addition of carbon dioxide, or iswithin 50, 40, 30, 20, 10, 8, 5, 4, 3, 2, 1, 0.5, or 0.1% of apredetermined desired value. In certain embodiments, the addition ofcarbon dioxide, components of the concrete mix, and/or additionalcomponents such as one or more admixtures, may be adjusted so thatcompactability and/or 1-, 7-, and/or 28-day strength of the finalconcrete mix of the final concrete mix is within 10% of thecompactability and/or 1-, 7-, and/or 28-day strength of the finalconcrete mix that would be achieved without the addition of carbondioxide. In certain embodiments, the addition of carbon dioxide,components of the concrete mix, and/or additional components such as oneor more admixtures, may be adjusted so that compactability and/or 1-,7-, and/or 28-day strength of the final concrete mix is within 5% of thecompactability and/or 1-, 7-, and/or 28-day strength of the finalconcrete mix that would be achieved without the addition of carbondioxide. In certain embodiments, the addition of carbon dioxide,components of the concrete mix, and/or additional components such as oneor more admixtures, may be adjusted so that compactability and/or 1-,7-, and/or 28-day strength of the final concrete mix is within 2% of thecompactability and/or 1-, 7-, and/or 28-day strength of the finalconcrete mix that would be achieved without the addition of carbondioxide. Other limits and ranges of compactability and/or 1-, 7-, and/or28-day strength of the final concrete mix, as described herein, may alsobe used. Any suitable measurement method for determining compactabilityand/or 1-, 7-, and/or 28-day strength of the final concrete mix may beused, and standard techniques are well-known in the art. In certainembodiments, in addition to the desired compactability and/or 1-, 7-,and/or 28-day strength of the final concrete mix, one or more additionalcharacteristics are achieved, such as that shrinkage is within certaindesired ranges, or above or below certain threshold numbers, asdetermined by standard methods in the art. In all cases, if theoperation is a wet cast operation, additionally, or alternatively,flowability may be modulated, e.g., by use of one or more admixtures,for example so that flowability is within 50, 40, 30, 20, 10, 8, 5, 4,3, 2, 1, 0.5, or 0.1% of the value or values that would be achievedwithout the addition of carbon dioxide, or within 50, 40, 30, 20, 10, 8,5, 4, 3, 2, 1, 0.5, or 0.1% of a predetermined value. Any suitableadmixture, as described herein, may be used. In certain embodiments theadmixture comprises a set retarder. In certain embodiments, theadmixture comprises a carbohydrate, such as a saccharide, e.g., a sugaror sugar derivative. In certain embodiments, the admixture is selectedfrom the group consisting of fructose, sodium glucoheptonate, and sodiumgluconate. In certain embodiments, the admixture is sodium gluconate,e.g., sodium gluconate delivered to achieve a percentage, per weight ofcement, of 0.05-0.8%, 0.1-0.8%, or 0.1-0.6%, or 0.1-0.5%, or 0.2-0.5%,or 0.2-3%, or 0.2-2%, or 0.2-1%. In certain embodiments a secondadmixture is also used, such as any of the admixtures described herein.

In certain embodiments, the mixer is a transportable mixer.“Transportable mixer,” as that term is used herein, includes mixers intowhich components of a cement mix, e.g., hydraulic cement mix are placedin one location and the cement mix, e.g., hydraulic cement mix istransported to another location which is remote from the first location,then used. A transportable mixer is transported by, for example, road orrail. As used herein, a transportable mixer is not a mixer such as thoseused in a pre-cast concrete operations. Thus, in certain embodiments,the mixer may be the drum of a ready-mix truck in which a concrete mixis prepared for delivery to a worksite. In this case, the mixer isconfigured to mix concrete and to deliver it to a worksite, and theaddition of carbon dioxide to the concrete mix, the components of theconcrete mix, and, optionally, other ingredients such as one or moreadmixtures, are adjusted so that a desired level of flow of the cementmix, e.g., hydraulic cement mix, i.e., concrete, generally a level offlow that is similar to the level that would be present without theaddition of the carbon dioxide, or a predetermined flowability, isachieved, and so that the final product after pouring at the worksitepossesses a desired hardening time, strength, shrinkage, and othercharacteristics as desired. In the case of the ready-mix mixer, theaddition of carbon dioxide, components of the concrete mix, and/oradditional components such as one or more admixtures, may be adjusted sothat flowability of the final concrete mix is within 50, 40, 30, 20, 10,8, 5, 4, 3, 2, 1, 0.5, or 0.1% of the flowability that would be achievedwithout the addition of carbon dioxide, or a predetermined flowability.In certain embodiments, the addition of carbon dioxide, components ofthe concrete mix, and/or additional components such as one or moreadmixtures, may be adjusted so that flowability of the final concretemix is within 10% of the flowability that would be achieved without theaddition of carbon dioxide, or a predetermined flowability. In certainembodiments, the addition of carbon dioxide, components of the concretemix, and/or additional components such as one or more admixtures, may beadjusted so that flowability of the final concrete mix is within 5% ofthe flowability that would be achieved without the addition of carbondioxide, or a predetermined flowability. In certain embodiments, theaddition of carbon dioxide, components of the concrete mix, and/oradditional components such as one or more admixtures, may be adjusted sothat flowability of the final concrete mix is within 2% of theflowability that would be achieved without the addition of carbondioxide, or a predetermined flowability. Other limits and ranges offlowability, as described herein, may also be used. Any suitablemeasurement method for determining flowability may be used, such as thewell-known slump test. In certain embodiments, in addition to thedesired flowability, one or more additional characteristics areachieved, such as that shrinkage and/or strength, such as compressivestrength, at one or more times after pouring of the concrete are withincertain desired ranges, or above or below certain threshold numbers, asdetermined by standard methods in the art. The addition of carbondioxide, components of the concrete mix, and/or additional componentssuch as one or more admixtures, may be adjusted so that 1-, 7-, 28,and/or 56-day strength of the final concrete mix is within 50, 40, 30,20, 10, 8, 5, 4, 3, 2, 1, 0.5, or 0.1% of the value or values that wouldbe achieved without the addition of carbon dioxide, or a predeterminedstrength value. In certain embodiments, the addition of carbon dioxide,components of the concrete mix, and/or additional components such as oneor more admixtures, may be adjusted so that 1-, 7-, 28, and/or 56-daystrength of the final concrete mix of the final concrete mix is within10% of the 1-, 7-, 28 and/or 56-day strength of the final concrete mixthat would be achieved without the addition of carbon dioxide, or apredetermined strength value. In certain embodiments, the addition ofcarbon dioxide, components of the concrete mix, and/or additionalcomponents such as one or more admixtures, may be adjusted so that 1-,7-, 28 and/or 56-day strength of the final concrete mix is within 5% ofthe 1-, 7-, 28 and/or 56-day strength of the final concrete mix thatwould be achieved without the addition of carbon dioxide, or apredetermined strength value. In certain embodiments, the addition ofcarbon dioxide, components of the concrete mix, and/or additionalcomponents such as one or more admixtures, may be adjusted so that 1-,7-, 28 and/or 56-day strength of the final concrete mix is within 2% ofthe 1-, 7-, 28 and/or 56-day strength of the final concrete mix thatwould be achieved without the addition of carbon dioxide, or apredetermined strength value. Other limits and ranges of 1-, 7-, 28and/or 56-day strength of the final concrete mix, as described herein,may also be used. Any suitable measurement method for determining 1-,7-, 28 and/or 56-day strength of the final concrete mix may be used, andstandard techniques are well-known in the art. In certain embodiments,in addition to the desired 1-, 7-, 28 and/or 56-day strength of thefinal concrete mix, one or more additional characteristics are achieved,such as that shrinkage is within certain desired ranges, or above orbelow certain threshold numbers, as determined by standard methods inthe art. Any suitable admixture, as described herein, may be used. Incertain embodiments the admixture comprises a set retarder. In certainembodiments, the admixture comprises a carbohydrate, such as asaccharide, e.g., a sugar. In certain embodiments, the admixture isselected from the group consisting of fructose, sodium glucoheptonate,and sodium gluconate. In certain embodiments, the admixture is sodiumgluconate, e.g., sodium gluconate at a percentage of 0.01-2%, or0.01-1%, or 0.01-0.8%, or 0.01-0.5%, or 0.01-0.1%, or 0.1-0.8%, or0.1-0.6%, or 0.1-0.5%, or 0.2-0.5%, or 0.2-3%, or 0.2-2%, or 0.2-1%. Incertain embodiments, the admixture is fructose, e.g., fructose at apercentage of 0.01-2%, or 0.01-1%, or 0.01-0.8%, or 0.01-0.5%, or0.01-0.1%, or 0.1-0.8%, or 0.1-0.6%, or 0.1-0.5%, or 0.2-0.5%, or0.2-3%, or 0.2-2%, or 0.2-1%. In certain embodiments a second admixtureis also used, such as any of the admixtures described herein.

It will be appreciated that, both in the case of a wet cast (such asreadymix) or a dry cast, different mixes may require different treatmentin order to achieve a desired flowability and/or compactability, andthat mix types may be tested in advance and proper treatment, e.g.,proper type and/or percentage of admixture determined. In certain casesadmixture may not be required; indeed, with certain mix types and carbondioxide concentrations, compactability (strength) or floawability may bewithin acceptable limits; e.g., strength may even be improved in certainmix types at certain levels of carbon dioxide addition. Also, the pointin the procedure in which ingredients are introduced can affect one ormore characteristics of the product, as can be determined in routinetesting and mix adjustment.

The mixer may be closed (i.e., completely or substantially completelyairtight) or open (e.g., the drum of a ready mix truck, or a precastmixer with various leack points). The mixer may be one of a plurality ofmixers, in which different portions of a cement mix, e.g., hydrauliccement mix are mixed, or it may be a single mixer in which the entirecement mix, e.g., hydraulic cement mix, such as a concrete mix, exceptin some cases additional water, is mixed.

Methods of Carbon Dioxide Delivery

Any suitable mixer for mixing concrete in an operation to produceconcrete for use in objects, such as for use in producing buildingmaterials, may be used. In some cases a mixer may be used where thedesired dose or uptake of carbon dioxide may be achieved using gasdelivery alone. For example, in most pre-cast mixers, the mixer isenclosed but not gas-tight (i.e., not open to the atmosphere, althoughnot gas tight, such that leak points are available for, e.g., carbondioxide sensors) and the head space and mixing times are such that adesired dose or uptake can be achieved with nothing more than gaseouscarbon dioxide delivery.

In some cases, however, such as in a ready mix truck where head space isrelative less than in a typical precast mixer, additional efficiency maybe desired, or necessary, in order to achieve a desired carbon dioxidedose or uptake. In these cases, the use of carbon dioxide-charged mixwater, or liquid carbon dioxide delivered so as to form a gas and asolid, or addition of solid carbon dioxide, or any combination thereof,may be used. The carbon dioxide may be delivered to the mixer as aliquid which, through proper manipulation of delivery, such as flow rateand/or orifice selection, becomes a mixture of gaseous carbon dioxideand solid carbon dioxide upon delivery, for example, in an approximate1:1 ratio. The gaseous carbon dioxide is immediately available foruptake into the cement mix, e.g., hydraulic cement mix, while the solidcarbon dioxide effectively serves as a time-delayed delivery of gaseouscarbon dioxide as the solid gradually sublimates to gas. Additionally,or alternatively, carbon dioxide-charged mix water may be used. Carbondioxide-charged water is routinely used in, e.g., the soda industry, andany suitable method of charging the mix water may be used. The water maybe charged to achieve a carbon dioxide concentration of at least 1, 2,3, 4, 5, 6, 7, 8, 9, or 10 g CO₂/L water. Carbon dioxide-charged mixwater can deliver a significant portion of the desired carbon dioxidedose for a cement mix, e.g., hydraulic cement mix, for example, at least5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90,or 95% of the total carbon dioxide delivered to a batch of cement mix,e.g., hydraulic cement mix may be delivered in the mix water. In somecases, 100% of the carbon dioxide may be delivered in the mix water. Insome cases, at least 20% of the carbon dioxide is delivered in the mixwater. In some cases, at least 30% of the carbon dioxide is delivered inthe mix water. Without being bound by theory, it is thought that thecarbon dioxide thus delivered reacts rapidly with components of thecement mix, e.g., hydraulic cement mix, allowing further uptake ofgaseous carbon dioxide by the water. Carbon dioxide may also bedelivered in solid form, i.e., as dry ice, directly, as describedelsewhere herein.

A ready mix operation is an example of a system where it may bedesirable to use one or both of carbon dioxide-charged water and liquidcarbon dioxide delivery. A ready mix truck drum is open to theatmosphere and has a relatively small head space in comparison to themass of concrete, which is typically 6 to 10 cubic meters when the truckis batched to capacity, which it is as often as possible. Mixing time atthe batching site may be relatively short. Therefore the use ofcarbonated mix water and liquid CO₂ may be used to ensure that a desireddose of CO₂ is delivered. For example, in a ready mix operation in whicha carbon dioxide delivery of 1.5% is desired: The volume of gas to beadded is ˜2.66 m³ of gas/m³ of concrete (assuming 350 kg/m³ of cementbeing carbonated at 1.5%). Mix water is typically represented by addedwater and excess moisture contained in the aggregate. If the free mixwater (˜160 L/m³) is carbonated with CO₂ using existing carbonationtechnology, such as that used in the soda industry, to 10 g of CO₂/L ofwater this represents approximately ⅓ of the target carbon dioxidedelivery of 1.5% bwc. Contact with cement results in rapid carbonationof the dissolved CO₂, and the water is quickly ready for additionalcarbon dioxide dissolution once it is in the truck and in contact withthe cement. The use of carbon dioxide in the mix water reduces the totalcarbon dioxide to be added to the truck to 3.66 kg of CO₂ (or about 1.85m³ gas/m³ concrete). This amount may still be too high to be universallydelivered in atmospheric pressure gas form. Therefore liquid CO₂injection into the truck can be used for the balance of the carbondioxide supply. Liquid CO₂ injection of the remaining 3.66 kg CO₂/m³ inthe truck can be done using a controlled flow rate that is based uponsensors and a calibrated CO₂ uptake rate. See Control Mechanisms asdescribed herein. Upon delivery through a nozzle the liquid transformsinto a mixture of solid and gaseous carbon dioxide. The liquid deliverycan result, e.g., in 1.75 kg of solid CO₂ snow (with a density of 1560kg/m³) and 1.9 kg of CO₂ gas (0.96 m³ gas). The gas is immediately beavailable for uptake by the mix water while the solid CO₂ serves as atime delayed CO₂ delivery, as the solid gradually sublimates to gas.This process reduces the gaseous volume injected into the truck toapproximately 29% of the volume needed if the entire CO₂ delivery hadbeen via gaseous CO₂. In some cases part of the concrete mix, e.g., theaggregate, may also be wet. In that case, less mix water is used andcorrespondingly more liquid carbon dioxide. Moisture sensors, e.g., tosense the moisture content of the aggregate, may be used to provideinformation to allow for the adjustment, even on a batch-by-batch basis.This approach can allow for higher uptake rates and greater efficiency.

Exemplary embodiments include a method for producing a cement mix, e.g.,hydraulic cement mix comprising (i) placing components of the cementmix, e.g., hydraulic cement mix in a mixer and mixing the components;and (ii) delivering liquid CO₂ via an opening in a conduit into themixer in such a manner as to cause the liquid CO₂ to form a mixture ofgaseous and solid CO₂ which then contact the cement mix, e.g., hydrauliccement mix. The delivery of the liquid may be controlled in such amanner, e.g., by adjusting flow rate and/or orifice, or other suitablemeans, as to form a mixture of gaseous to solid carbon dioxide in aratio in the range of 1:10 to 10:1, or 1:5 to 5:1, or 1:3 to 3:1, or 1:2to 2:1, or 1:1.5 to 1.5:1, or 1:1.2 to 1.2 to 1. The cement mix, e.g.,hydraulic cement mix comprises water and the water may be charged withCO₂ before delivery to the mixer as described herein, for example to alevel of at least 2 g CO₂/L water, or at least 4 g CO₂/L water, or atleast 6 g CO₂/L water, or at least 8 g CO₂/L water, or at least 9 gCO₂/L water, or at least 10 g CO₂/L water. The mixer may be any suitablemixer, such as a stationery mixer or a transportable mixer, e.g., thedrum of a ready mix concrete truck. When the mixer is the drum of aready mix concrete truck, the liquid CO₂ may be supplied to the mixer ata batching plant, or it may be supplied to the mixer during transport ofthe batch to a job site, or even at the job site itself, or acombination thereof. The method may further include monitoring acharacteristic of the cement mix, e.g., hydraulic cement mix, a gasmixture in contact with the cement mix, e.g., hydraulic cement mix, acomponent of a cement mix, e.g., hydraulic cement mix apparatus, or acomponent exposed to the cement mix, e.g., hydraulic cement mix, andmodulating the flow of liquid CO₂ according to the characteristicmonitored. For example, CO₂ concentration, temperature, moisturecontent, rheology, pH, or a combination thereof may be monitored, asdetailed elsewhere herein. When CO₂ is monitored, it may be monitored ina portion of gas outside the mixer, e.g. at a leak point or spill point.

Exemplary embodiments also include a method for producing a cement mix,e.g., hydraulic cement mix comprising (i) contacting components of thecement mix, e.g., hydraulic cement mix with CO₂-charged water, whereinthe water is charged with CO₂ to a level of at least 2 g/L, 3 g/L, 4g/L, 6 g/L, 8 g/L, 9 g/L, or 10 g/L, and mixing the components and thewater. Embodiments further include a method of producing a carbonatedcement mix, e.g., hydraulic cement mix comprising (i) determining a doseof CO₂ to be delivered to the cement mix, e.g., hydraulic cement mix;and (ii) delivering at least 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100%of the dose of CO₂ as CO₂ dissolved in mix water for the cement mix,e.g., hydraulic cement mix. In certain embodiments the dose is 0.1-10%,or 0.5-5%, or 0.5-4%, or 0.5-3%, or 0.5-2%, or 1-5%, or 1-4%, or 1-3%,or 1-2% CO₂ bwc. In certain embodiments the dose is 1.5% CO₂ bwc.Delivery of carbon dioxide-charged mix water as described may becombined in some embodiments with delivery of gaseous and/or liquidcarbon dioxide.

Exemplary embodiments further include an apparatus for carbonating acement mix, e.g., hydraulic cement mix comprising (i) a mixer for mixingthe cement mix, e.g., hydraulic cement mix; (ii) a source of liquid CO₂;and (iii) a conduit operably connecting the source of liquid CO₂ to themixer, wherein the conduit comprises an orifice through which the liquidCO₂ exits the conduit into the mixer. The conduit can include a systemfor regulating the flow of the liquid CO₂ where the system, the orifice,or both, are configured to deliver the liquid CO₂ as a combination ofsolid and gaseous CO₂, such as by regulating flow rate of the liquid CO₂and/or orifice configuration, such as to produce a ratio of solid togaseous CO₂ in the range of 1:10 to 10:1, or 1:5 to 5:1, or 1:3 to 3:1,or 1:2 to 2:1, or 1:1.5 to 1.5:1, or 1:1.2 to 1.2 to 1, for example,between 1:3 and 3:1, or between 1:2 and 2:1. The mixer can be atransportable mixer, such as a drum of a ready-mix truck. The source ofliquid CO₂ and the conduit may remain at a batching facility after thetransportable is charged, or may accompany the transportable mixer whenthe transportable mixer transports the cement mix, e.g., hydrauliccement mix. The apparatus may further include a system for deliveringCO₂-charged water to the mixer comprising a source of CO₂-charged waterand a conduit operably connected to the source and configured to deliverthe water to the mixer, which may in some cases further include acharger for charging the water with CO₂. In certain cases the mixer istransportable and the system for delivering CO₂-charged water to themixer is detachable from the mixer during transport, e.g., if the mixeris the drum of a ready mix truck the system for delivering and,optionally, charging CO₂-charged water remains at the batching facility.

Exemplary embodiments also include an apparatus for producing acarbonated cement mix, e.g., hydraulic cement mix comprising (i) a mixerfor mixing the cement mix, e.g., hydraulic cement mix; and (ii) at leasttwo of (a) a source of gaseous CO₂ operably connected to the mixer andconfigured to deliver gaseous CO₂ to the mixer; (b) a source of liquidCO₂ operably connected to the mixer and configured to deliver liquid CO₂to the mixer and release the liquid CO₂ into the mixer as a mixture ofgaseous and solid CO₂; and (c) a source of carbonated water operablyconnected to the mixer and configured to deliver carbonated water to themixer.

E. Retrofitting Existing Apparatus

In certain embodiments, the methods of the invention include methods andapparatus for retrofitting an existing cement mix, e.g., hydrauliccement mix apparatus to allow for the contact of the mixing cement mix,e.g., hydraulic cement mix with carbon dioxide. As used herein, the term“retrofit” is used in its generally accepted sense to mean installingnew or modified parts or equipment into something previouslymanufactured or constructed. The retrofit may modify the existingapparatus to perform a function for which it was not originally intendedor manufactured. In the case of the present invention, a cement mix,e.g., hydraulic cement mix apparatus to be retrofitted is not originallyconstructed to allow addition of carbon dioxide to a cement mix, e.g.,hydraulic cement mix during mixing of the cement mix, e.g., hydrauliccement mix. Preferably, the retrofitting requires little or nomodification of the existing apparatus. The retrofitting may includedelivering to a site where a pre-existing cement mix, e.g., hydrauliccement mix apparatus is located the components necessary to modify theexisting cement mix, e.g., hydraulic cement mix apparatus to allowexposure of a cement mix, e.g., hydraulic cement mix to carbon dioxideduring mixture. Instructions for one or more procedures in theretrofitting may also be transported or transmitted to the site of theexisting cement mix, e.g., hydraulic cement mix apparatus.

The retrofitting may include installing components necessary to modifythe existing cement mix, e.g., hydraulic cement mix apparatus to allowexposure of a cement mix, e.g., hydraulic cement mix to carbon dioxideduring mixing. The components may include a conduit for delivery ofcarbon dioxide to a cement mix, e.g., hydraulic cement mix mixer. Thecomponents may further include a source of carbon dioxide. In systems inwhich a control system is included, the retrofit may include modifyingthe existing control system of the cement mix, e.g., hydraulic cementmix apparatus to perform functions appropriate to the controlledaddition of carbon dioxide to the cement mix, e.g., hydraulic cementmix. Instructions for such modifications may also be transmitted or sentto the site of the existing cement mix, e.g., hydraulic cement mixapparatus controller. Such modifications can include, for example,modifying the existing controller settings to include timing the openingand closing of a gas supply valve to deliver a flow of carbon dioxide ata predetermined flow rate for a predetermined time from the carbondioxide source via the conduit to the mixer at a certain stage in thehydraulic mix apparatus operations. They may also include modifying thecontroller to modify the timing and/or amount of water addition to thecement mix, e.g., hydraulic cement mix, addition of admixture, and anyother suitable parameter. Alternatively, or in addition to, modifyingthe existing controller, the retrofitting may include providing one ormore new controllers to the pre-existing cement mix, e.g., hydrauliccement mix apparatus. The retrofitting can include transporting the newcontroller or controllers to the site of the existing cement mix, e.g.,hydraulic cement mix apparatus. In addition, one or more sensors, suchas sensors for sensing the positions and/or states of one or morecomponents of the existing cement mix, e.g., hydraulic cement mixapparatus, which were not part of the original manufactured equipment,may be installed. The retrofit may include transporting one or moresensors to the site of the existing cement mix, e.g., hydraulic cementmix apparatus. Actuators, which may be actuators in the retrofittedapparatus, e.g., a gas supply valve, or in the original equipment, e.g.,to move or start or stop various operations such as addition of water,may be operably connected to the retrofitted controller in order tomodify the operations of the cement mix, e.g., hydraulic cement mixapparatus according to the requirements of contacting the cement mix,e.g., hydraulic cement mix with carbon dioxide. The retrofit may includetransporting one or more sensors to the site of the existing cement mix,e.g., hydraulic cement mix apparatus.

III. Methods

In certain embodiments, the invention provides methods for producing acarbonated cement mix in a mix operation in a cement mix apparatuscomprising (i) contacting a cement mix comprising cement binder andaggregate in a mixer with carbon dioxide while the cement mix is mixing;(ii) monitoring a characteristic of the cement binder, the cement mix, agas mixture in contact with the cement mix or the mixer, or a componentof the cement mix apparatus; and (iii) modulating the exposure of thecement mix to the carbon dioxide or another characteristic of the cementmix operation, or a combination thereof according to the characteristicmonitored in step (ii). In some cases, only exposure of the cement mixto the carbon dioxide is modulated; in other cases, only anothercharacteristic of the cement mix operation is modulated; and in othercases, both are modulated.

The cement binder may be any suitable cement binder as described herein,i.e., a cement binder containing calcium species capable of reactingwith carbon dioxide to form stable or metastable reaction products, suchas carbonates. The cement binder may be a hydraulic cement, for example,a Portland cement. “Cement mix,” as that term is used herein, includes amix of a cement binder, e.g., a hydraulic cement, such as a Portlandcement, with aggregate; “concrete” is generally synonomous with “cementmix” as those terms are used herein.

The mix operation may be any operation in which a cement mix/concrete isproduced for any of the various uses known in the art for such a mix.Thus, the cement mix operation may be an operation in a mixer at aprecast facility for producing a cement mix for use in a dry cast or wetcast operation. In other embodiments, the cement mix operation may be anoperation in a mixer for a ready mix operation, e.g., the drum of aready mix truck. Any other suitable cement mix operation may also beused, so long as it is amenable to addition of carbon dioxide to thecement mix during mixing, for example, a mixer on site at a constructionsite. Thus, additional examples include pug mill or twin shaftcontinuous mixers that can be used for roller compacted concrete (drymix) or CTB (cement treated base) for road stabilization, which arecontinuous mix applications rather than batch. While some of the aspectsof water proportioning might not be achievable there still exists thepossibility to add CO₂ during the mixing step.

The characteristic monitored may be any suitable characteristic thatprovides useful feedback to inform modulation of exposure of the cementmix to carbon dioxide or another characteristic of the cement mixoperation. In certain embodiments, the characteristic monitored is (a)mass of cement binder added to the cement mix, (b) location of thecement binder in the mix apparatus (e.g., coordinating carbon dioxidedelivery with delivery of cement binder; may be achieved by sensing thelocation of the cement mix or by timing of the mix sequence, which canbe input to the controller), (c) carbon dioxide content of a gas mixturewithin the mixer in contact with the cement mix, (d) carbon dioxidecontent of a gas mixture exiting from the mixer, (e) carbon dioxidecontent of gas mixture in the vicinity of the mix apparatus, (f)temperature of the cement mix or a component of the mix apparatus incontact with the cement mix, (g) rheology of the cement mix, (h)moisture content of the cement mix, or (i) pH of the cement mix. Thelocation of water in the mix apparatus also be monitored, e.g., todetermine when water addition is complete. These characteristics andmethods and apparatus for monitoring them are as described elsewhereherein. When the mass of the cement binder is monitored, the totalamount of carbon dioxide to be added to the cement mix may be modulatedto accord with a predetermined desired exposure, e.g., if a 1.5% carbondioxide/cement exposure is desired, the exact mass used in a particularbatch may be used to determine the exact total carbon dioxide to beadded to the batch (which may be used as is, or modified in response toother characteristics that are monitored). When location of the cementbinder or water in the mix apparatus is monitored, the modulation ofcarbon dioxide flow may be a simple on/off, e.g., when the cement mixand/or water is determined to have entered the mixer, carbon dioxideflow may be turned on at that time or at a predetermined time after thattime. In certain embodiments, the characteristic monitored in step (ii)comprises carbon dioxide content of a gas mixture exiting from themixer, e.g., at a leak point of the mixer. In this embodiment, and/or inother embodiments in which a carbon dioxide content of a gas mixture ismonitored, the exposure of the cement mix to carbon dioxide can bemodulated when the carbon dioxide content of the gas mixture reaches athreshold value, and/or when the rate of change of the carbon dioxidecontent of the gas mixture reaches a threshold value. The modulation canbe an increase in the rate of carbon dioxide addition to the cement mix,a decrease, or even a full stop. In certain embodiments, thecharacteristic monitored is the temperature of the cement mix or acomponent of the mix apparatus in contact with the cement mix. Forexample, a wall of the mixer may be monitored for temperature. Theexposure of the cement mix to carbon dioxide can be modulated when thetemperature of the cement mix or a component of the mix apparatus incontact with the cement mix, or a combination of a plurality of suchtemperatures, reaches a threshold value and/or when the rate of changeof the temperature of the cement mix or a component of the mix apparatusin contact with the cement mix reaches a threshold value. If temperatureis used as a measure for the threshold value, it may be an absolutetemperature, or it may be a temperature relative to the temperature ofthe mix before the addition of carbon dioxide, e.g., a temperature thatis a certain number of degrees above the starting temperature, forexample 10-50° C. above the starting value, or 10-40° C. above thestarting value, or 10-30° C. above the starting value. The exactdifference between starting and threshold temperature may bepredetermined for a particular mix recipe by determining therelationship between carbonation and temperature for that recipe, or forthat particular cement binder in relation to other components of thatrecipe.

In certain embodiments, a plurality of characteristics of the cementbinder, the cement mix, a gas mixture in contact with the cement mix orthe mixer, or a component of the cement mix apparatus are monitored,e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, or 10 characteristics, forexample, at least 2 characteristics. In certain embodiments, at least 2of (a) mass of cement binder added to the cement mix, (b) location ofthe cement binder in the mix apparatus, (c) carbon dioxide content of agas mixture within the mixer in contact with the cement mix, (d) carbondioxide content of a gas mixture exiting from the mixer, (e) carbondioxide content of gas mixture in the vicinity of the mix apparatus, (f)temperature of the cement mix or a component of the mix apparatus incontact with the cement mix, (g) rheology of the cement mix, (h)moisture content of the cement mix, or (i) pH of the cement mix aremonitored. In certain embodiments, at least 3 of (a) mass of cementbinder added to the cement mix, (b) location of the cement binder in themix apparatus, (c) carbon dioxide content of a gas mixture within themixer in contact with the cement mix, (d) carbon dioxide content of agas mixture exiting from the mixer, (e) carbon dioxide content of gasmixture in the vicinity of the mix apparatus, (f) temperature of thecement mix or a component of the mix apparatus in contact with thecement mix, (g) rheology of the cement mix, (h) moisture content of thecement mix, or (i) pH of the cement mix are monitored. In certainembodiments, at least 4 of (a) mass of cement binder added to the cementmix, (b) location of the cement binder in the mix apparatus, (c) carbondioxide content of a gas mixture within the mixer in contact with thecement mix, (d) carbon dioxide content of a gas mixture exiting from themixer, (e) carbon dioxide content of gas mixture in the vicinity of themix apparatus, (f) temperature of the cement mix or a component of themix apparatus in contact with the cement mix, (g) rheology of the cementmix, (h) moisture content of the cement mix, or (i) pH of the cement mixare monitored. In certain embodiments, at least 5 of (a) mass of cementbinder added to the cement mix, (b) location of the cement binder in themix apparatus, (c) carbon dioxide content of a gas mixture within themixer in contact with the cement mix, (d) carbon dioxide content of agas mixture exiting from the mixer, (e) carbon dioxide content of gasmixture in the vicinity of the mix apparatus, (f) temperature of thecement mix or a component of the mix apparatus in contact with thecement mix, (g) rheology of the cement mix, (h) moisture content of thecement mix, or (i) pH of the cement mix are monitored. In certainembodiments, at least 6 of (a) mass of cement binder added to the cementmix, (b) location of the cement binder in the mix apparatus, (c) carbondioxide content of a gas mixture within the mixer in contact with thecement mix, (d) carbon dioxide content of a gas mixture exiting from themixer, (e) carbon dioxide content of gas mixture in the vicinity of themix apparatus, (f) temperature of the cement mix or a component of themix apparatus in contact with the cement mix, (g) rheology of the cementmix, (h) moisture content of the cement mix, or (i) pH of the cement mixare monitored.

In certain embodiments, the method alternatively, or additionally,include monitoring the time of exposure of the cement mix to the carbondioxide, the flow rate of the carbon dioxide, or both.

When an additional characteristic of the mix operation is modulated inresponse to the monitoring, it may be any suitable characteristic. Incertain embodiments, the additional characteristic includes (a) whetheror not an admixture is added to the cement mix, (b) type of admixtureadded to the cement mix, (c) timing of addition of admixture to thecement mix, (d) amount of admixture added to the cement mix, (e) amountof water added to the cement mix, (f) timing of addition of water to thecement mix, (g) cooling of the cement mix during or after carbon dioxideaddition, or a combination thereof. If an admixture is used, it may beany suitable admixture for adjusting a characteristic of the cement mix,e.g., an admixture to adjust the rheology (flowability) of the mix, forexample, in a wet cast operation. Examples of suitable admixtures aredescribed herein, e.g., carbohydrates or carbohydrate derivatives, suchas sodium gluconate.

The characteristic may be monitored by any suitable means, such as by byone or more sensors. Such sensors may transmit information regarding thecharacteristic to a controller which processes the information anddetermines if a modulation of carbon dioxide exposure or anothercharacteristic of the mix operation is required and, if so, transmits asignal to one or more actuators to carry out the modulation of carbondioxide exposure or other characteristic of the mix operation. Thecontroller may be at the site of the mix operation or it may be remote.Such sensors, controllers, and actuators are described further elsewhereherein. If a controller is used, it may store and process theinformation obtained regarding the characteristic monitored in step (ii)for a first batch of cement mix and adjust conditions for a subsequentsecond cement mix batch based on the processing. For example, thecontroller may adjust the second mix recipe, e.g., amount of water usedor timing of water addition, or carbon dioxide exposure in the secondbatch to improve carbon dioxide uptake, or to improve rheology or othercharacteristics of the mix, e.g., by addition and/or amount of anadmixture, and/or timing of addition of the admixture. In suchembodiments in which one or more conditions of a second mix operationare adjusted, in certain embodiments the one or more conditions of thesecond mix operation includes (a) total amount of carbon dioxide addedto the cement mix, (b) rate of addition of carbon dioxide, (c) time ofaddition of carbon dioxide to the cement mix, (d) whether or not anadmixture is added to the cement mix, (e) type of admixture added to thecement mix, (f) timing of addition of admixture to the cement mix, (g)amount of admixture added to the cement mix, (h) amount of water addedto the cement mix, (i) timing of addition of water to the cement mix,(j) cooling the cement mix during or after carbon dioxide addition, or acombination thereof. The controller can also receive additionalinformation regarding one or more characteristics of the cement mixmeasured after the cement mix leaves the mixer, and adjusts conditionsfor the second cement mix batch based on processing that furthercomprises the additional information. In certain embodiments, the one ormore characteristics of the cement mix measured after the cement mixleaves the mixer comprises (a) rheology of the cement mix at one or moretime points, (b) strength of the cement mix at one or more time points,(c) shrinkage of the cement mix, (d) water absorption of the cement mix,or a combination thereof. Other characteristics include elastic modulus,density, and permeability. Any other suitable characteristic, as knownin the art, may be measured. The characteristic monitored can depend onthe requirements for a particular mix batch, although othercharacteristics may also be monitored to provide data to the controllerfor future batches in which those characteristics would be required.

In embodiments in which a controller adjusts conditions for a second mixoperation based on input from a first mix operation, the second mixoperation may be in the same mix facility or it may be in a differentmix facility. In certain embodiments, the controller, one or moresensors, one or more actuators, or combination thereof, transmitsinformation regarding the characteristics monitored and conditionsmodulated to a central controller that receives information from aplurality of controllers, sensors, actuators, or combination thereof,each of which transmits information from a separate mixer to the centralcontroller. Thus, for example, a first mix facility may have a firstsensor to monitor a first characteristic of the first mix operation, anda second mix facility may have a second sensor to monitor a secondcharacteristic of a second mix operation, and both may send informationregarding the first and second characteristics to a central controller,which processes the information and transmit a signal to the first,second, or even a third mix operation to adjust conditions based on thefirst and second signals from the first and second sensors. Additionalinformation that will be typically transmitted to the central controllerincludes mix components for the mixes at the first and second mixoperations (e.g., type and amount of cement binder, amount of water andw/c ratio, types and amounts of aggregate, whether aggregate was wet ordry, admixtures, and the like) amount, rate, and timing of carbondioxide addition, and any other characteristic of the first and secondmix operations that would be useful for determining conditions tomodulate future mix operations based on the characteristics achieved inpast mix operations. Any number of mix operations may input informationto the central controller, e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, or 10mix operations, or at least 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, or100 mix operations. The central controller may also receive any otherinformation that may be suitable to informing decisions regarding mixoperations to optimize one or more conditions of the mix operationand/or of the cement mix produced in the operation. For example, thecentral controller may receive information from experiments conductedwith various types of cements (e.g., various types of Portland cements)carbonated under various conditions, and/or exposed to variousadmixtures, such as at different times, or in different concentrations,and the like, and the resulting characteristics of the cement mix, suchas rheology at one or more timepoints, strength at one or moretimepoints, and the like. Any other suitable information, such asinformation published in literature, or obtained in any manner, may beinput into the central controller. The information the centralcontroller receives can be processed and used to adjust cement mixoperations at any mix operation to which the central controller cantransmit outputs. Thus, the central controller can learn from numerousmix operations to optimize future operations and, over time, canaccumulate a database to inform decisions in mix operations at a mixsite even if a particular mix recipe and/or conditions have never beenused at that site. The central controller can match to past mix recipes,or predict optimum conditions for a new mix recipe based on suitablealgorithms using information in its database, or both.

In certain embodiments, the invention provides a method of carbonating acement mix in a mixer that is not completely airtight in such a way asto achieve an efficiency of carbonation of at least 60, 70, 80, 90, 95,96, 97, 98, or 99%, wherein efficiency of carbonation is the amount ofcarbon dioxide retained in the cement mix per the total amount of carbondioxide to which the cement mix is exposed during mixing. The mixer mayhave leak points and other aspects that make it less than airtights,such as seen in a typical mixer for a precast operation. The mixer maybe, e.g., the drum of a ready mix truck which has a large opening to theoutside atmosphere. Such efficiency may be achieved, e.g., by using anyof the methods to modulate the exposure of the cement mix to carbondioxide as detailed above.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting acement mix, e.g., hydraulic cement mix comprising a first portion ofwater and hydraulic cement in a mixer with carbon dioxide while thecement mix, e.g., hydraulic cement mix is mixing; and (ii) adding asecond portion of water to the cement mix, e.g., hydraulic cement mix.In some aspects of this embodiment, the contacting comprises directing aflow of carbon dioxide to the cement mix, e.g., hydraulic cement mix.The second portion of water may be added to the cement mix, e.g.,hydraulic cement mix during said flow or after said flow has ceased, forexample, after said flow has ceased. The method may include addingaggregate to the cement mix, e.g., hydraulic cement mix to produce aconcrete mix; in certain embodiments, the aggregate comprises some orall of the first portion of water. The aggregate may be added before thecontacting with the carbon dioxide. In certain embodiments, the methodincludes (iii) adding an admixture to the cement mix, e.g., hydrauliccement mix, such as an admixture that modulates the flowability of thecement mix, e.g., hydraulic cement mix. In embodiments in which anadmixture to modulate flowability is added, the admixture may added inan amount to achieve a flowability in a predetermined range offlowabilities, such as a predetermined range of flowabilities that isdetermined by allowing for a margin from the flowability of the cementmix, e.g., hydraulic cement mixture without the addition of carbondioxide. The admixture may be selected from the group consisting of apolycarboxylate superplasticer, a naphthalene HRWR, or any combinationthereof. In certain embodiments, the admixture contains sodiumgluconate, sucrose, glucose, molasses, corn syrup, EDTA, or acombination thereof. In certain embodiments, the admixture containssodium gluconate. In certain embodiments, the admixture containssucrose. In certain embodiments, the admixture contains glucose. Incertain embodiments, the admixture contains molasses. In certainembodiments, the admixture contains corn syrup. In certain embodiments,the admixture contains EDTA. In certain embodiments, the cement mix,e.g., hydraulic cement mix comprises Portland cement. Whether or not thecement mix, e.g., hydraulic cement mix comprises Portland cement, incertain embodiments cement mix, e.g., hydraulic cement mix comprisingthe first portion of water comprises an amount of water so that theratio of water to cement (w/c ratio) is equal to or less than 0.5. Incertain of these embodiments, the first portion of water comprises anamount of water so that the w/c ratio is in the range 0.1 to 0.5. thecarbon dioxide to which the cement mix, e.g., hydraulic cement mix isexposed may be at least 50% pure. The cement mix, e.g., hydraulic cementmix may be contacted with carbon dioxide by flowing carbon dioxide overthe surface of the mixing cement mix, e.g., hydraulic cement mix. Theflow of carbon dioxide directed to the cement mix, e.g., hydrauliccement mix, e.g., the surface of the mix, may last for 5 minutes orless, for example, the flow of carbon dioxide directed to the cementmix, e.g., hydraulic cement mix may last for 0.5-5 minutes. In certainembodiments, in which solid carbon dioxide is introduced into the cementmix, the solid carbon dioxide sublimates to gaseous carbon dioxide andthe delivery may be extended to more than 20, 30, 40, 50, or 60 minutes.The method may further comprise monitoring a characteristic of thecement mix, e.g., hydraulic cement mix, a gas mixture in contact withthe cement mix, e.g., hydraulic cement mix, a component of a cement mix,e.g., hydraulic cement mix apparatus, or a component exposed to thecement mix, e.g., hydraulic cement mix, and modulating the flow ofcarbon dioxide according to the characteristic monitored. For example,the method may further comprise monitoring a carbon dioxideconcentration in a portion of gas adjacent to the cement mix, e.g.,hydraulic cement mix, such as in a portion of gas in the mixer, or in aportion of gas outside the mixer, or both. The carbon dioxideconcentration may be monitored by a sensor. The sensor may transmit asignal to a controller. The controller may process the signal andtransmits a signal to an actuator according to the results of theprocessing, such as a controllable valve for controlling the flow ofcarbon dioxide to contact the cement mix, e.g., hydraulic cement mix. Inaddition to, or instead of carbon dioxide, a temperature of the cementmix, e.g., hydraulic cement mix, the mixer, or of another componentexposed to the cement mix, e.g., hydraulic cement mix may be monitored,for example, the temperature of the mixer may be monitored, or thetemperature of the cement mix, e.g., hydraulic cement mix inside themixer may be monitored, or the temperature of a portion of the cementmix, e.g., hydraulic cement mix that is transported outside the mixermay be monitored. The contacting of the cement mix, e.g., hydrauliccement mix with carbon dioxide may be modulated according to thetemperature monitored, for example, when the temperature beingmonitored, or a combination of temperatures being monitored, exceeds athreshold value. The threshold value may be a value determined relativeto the initial temperature of the cement mix, e.g., hydraulic cement mixbefore addition of carbon dioxide, such as a threshold temperature orrange of temperatures relative to the initial temperature as describedherein. Alternatively, the threshold value may be an absolute value. Thetemperature may be monitored by a sensor. The sensor may transmit asignal to a controller. The controller may process the signal andtransmit a signal to an actuator according to the results of theprocessing. The actuator may comprise a controllable valve forcontrolling the flow of carbon dioxide to contact the cement mix, e.g.,hydraulic cement mix. The method of contacting the hydraulic cement withcarbon dioxide may include, in any of these embodiments, controlling thecontacting of the cement mix, e.g., hydraulic cement mix with the carbondioxide is controlled to achieve a desired level of carbonation, such asa level as described herein, for example, at least 0.5, 1, 2, 3, or 4%.In certain embodiments, the exposure of the cement mix to carbon dioxideis modulated so as to provide an efficiency of carbon dioxide uptake ofat least 60, 70, 80, 90, 95, 96, 97, 98, or 99%, for example, at least70%.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting acement mix, e.g., hydraulic cement mix comprising water and hydrauliccement in a mixer with carbon dioxide while the cement mix, e.g.,hydraulic cement mix is mixing, wherein the carbon dioxide is contactedwith the surface of the cement mix, e.g., hydraulic cement mix bydirecting a flow of carbon dioxide to the surface of the mix fromoutside the mix, and wherein the flow lasts less than 5 min. In certainembodiments, the cement mix, e.g., hydraulic cement mix comprisesaggregate. The cement mix, e.g., hydraulic cement mix may furthercomprise an admixture. In certain embodiments, the mixer is atransportable mixer, such as a drum of a ready-mix truck. In certainembodiments, the mixer is a mixer for pre-cast concrete. The method mayfurther comprise controlling the flow of the carbon dioxide according tofeedback from one or more sensors that monitor a characteristic selectedfrom the group consisting of a characteristic of the cement mix, e.g.,hydraulic cement mix, a gas mixture in contact with the cement mix,e.g., hydraulic cement mix, a component of a cement mix, e.g., hydrauliccement mix apparatus, or a component exposed to the cement mix, e.g.,hydraulic cement mix.

In certain embodiments, the invention provides a method for producing ahydraulic cement mix comprising (i) contacting a cement mix, e.g.,hydraulic cement mix comprising water and hydraulic cement in a mixerwith carbon dioxide while the cement mix, e.g., hydraulic cement mix ismixing, wherein the carbon dioxide is contacted with the surface of thecement mix, e.g., hydraulic cement mix by directing a flow of carbondioxide to the surface of the mix from outside the mix, and wherein thecarbon dioxide is a component of a gaseous mixture that comprises atleast 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, or 99% carbon dioxide,such as at least 50% carbon dioxide. In certain embodiments, thehydraulic cement comprises aggregate. In certain embodiments, thehydraulic cement comprises an admixture. In certain embodiments, themixer is a transportable mixer, such as a drum of a ready-mix truck. Incertain embodiments, the mixer is a mixer for pre-cast concrete.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting acement mix, e.g., hydraulic cement mix in a mixer with carbon dioxidewhile the cement mix, e.g., hydraulic cement mix is mixing; and (ii)adding an admixture to the cement mix, e.g., hydraulic cement mix. Thecontacting may be achieved by directing a flow of carbon dioxide to thecement mix, e.g., hydraulic cement mix. In certain embodiments, theadmixture is an admixture that modulates the flowability of the cementmix, e.g., hydraulic cement mix. In certain of these embodiments, theadmixture may be added in an amount to achieve a flowability in apredetermined range of flowabilities, such as a predetermined range offlowabilities determined by allowing for a margin from the flowabilityof the cement mix, e.g., hydraulic cement mixture without the additionof carbon dioxide, for example, as described elsewhere herein. Incertain aspects of the fourth embodiment, the admixture is selected fromthe group consisting of a polycarboxylate superplasticer, a naphthaleneHRWR, or any combination thereof.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting acement mix, e.g., hydraulic cement mix in a mixer with carbon dioxidewhile the cement mix, e.g., hydraulic cement mix is mixing, wherein thecarbon dioxide is exposed to the cement mix, e.g., hydraulic cement mixwhen the w/c ratio of the cement mix, e.g., hydraulic cement mix is lessthan or equal to 0.4. In certain embodiments, the contacting is achievedby directing a flow of carbon dioxide to the cement mix, e.g., hydrauliccement mix. In certain aspects of this embodiment, the w/c ratio of thecement mix, e.g., hydraulic cement mix is 0.05-0.4. The method mayfurther comprise monitoring a characteristic of the cement mix, e.g.,hydraulic cement mix, a gas mixture in contact with the cement mix,e.g., hydraulic cement mix, a component of a cement mix, e.g., hydrauliccement mix apparatus, or a component exposed to the cement mix, e.g.,hydraulic cement mix, and modulating the flow of carbon dioxideaccording to the characteristic monitored. The method may comprise (ii)adding an admixture to the cement mix, e.g., hydraulic cement mix, suchas an admixture that modulates the flowability of the cement mix, e.g.,hydraulic cement mix, for example an admixture to modulate flowabilityof type and/or amount as described elsewhere herein.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting acement mix, e.g., hydraulic cement mix in a mixer with carbon dioxidewhile the cement mix, e.g., hydraulic cement mix is mixing at a firstlocation, and (ii) transporting the cement mix, e.g., hydraulic cementmix to a second location where the cement mix, e.g., hydraulic cementmix is used. In certain aspects of this embodiment, said contacting isachieved by directing a flow of carbon dioxide to the cement mix, e.g.,hydraulic cement mix. The second location may be at least 0.1 mile fromthe first location. The second location may be at least 0.5 mile fromthe first location. The method may comprise monitoring a characteristicof the cement mix, e.g., hydraulic cement mix, a gas mixture in contactwith the cement mix, e.g., hydraulic cement mix, a component of a cementmix, e.g., hydraulic cement mix apparatus, or a component exposed to thecement mix, e.g., hydraulic cement mix, and modulating the flow ofcarbon dioxide according to the characteristic monitored. The method maycomprise (ii) adding an admixture to the cement mix, e.g., hydrauliccement mix, such as an admixture that modulates the flowability of thecement mix, e.g., hydraulic cement mix.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting acement mix, e.g., hydraulic cement mix in a mixer with carbon dioxidewhile the cement mix, e.g., hydraulic cement mix is mixing with a flowof carbon dioxide directed to the cement mix, e.g., hydraulic cementmix, (ii) monitoring a characteristic of the cement mix, e.g., hydrauliccement mix, a gas mixture in contact with the cement mix, e.g.,hydraulic cement mix, a component of a cement mix, e.g., hydrauliccement mix apparatus, or a component exposed to the cement mix, e.g.,hydraulic cement mix; and (iii) modulating the exposure of the cementmix, e.g., hydraulic cement mix to the carbon dioxide according to thecharacteristic monitored in step (ii). The method may comprisemonitoring a carbon dioxide concentration in a portion of gas adjacentto the cement mix, e.g., hydraulic cement mix, e.g., a portion of gas inthe mixer, or a portion of gas outside the mixer. The carbon dioxideconcentration may be monitored by a sensor. The sensor may transmit asignal to a controller. The controller may process the signal andtransmit a signal to an actuator according to the results of theprocessing, for example, an actuator comprising a valve for controllingthe flow of carbon dioxide to contact the cement mix, e.g., hydrauliccement mix. The method may comprise monitoring a temperature of thecement mix, e.g., hydraulic cement mix, the mixer, or of anothercomponent exposed to the cement mix, e.g., hydraulic cement mix ismonitored. A temperature of the mixer may be monitored, or a temperatureof the cement mix, e.g., hydraulic cement mix inside the mixer may bemonitored, or a temperature of a portion of the cement mix, e.g.,hydraulic cement mix that is transported outside the mixer may bemonitored, or any combination thereof. The contacting of the cement mix,e.g., hydraulic cement mix with carbon dioxide may be modulatedaccording to the temperature monitored. The contacting of the cementmix, e.g., hydraulic cement mix with the carbon dioxide may be modulatedwhen the temperature being monitored, or a combination of temperaturesbeing monitored, exceeds a threshold value, such as a value determinedrelative to the initial temperature of the cement mix, e.g., hydrauliccement mix before addition of carbon dioxide, such as a threshold valueas described elsewhere herein. Alternatively, the threshold value may bean absolute value. The temperature may be monitored by a sensor. Thesensor may transmit a signal to a controller. The controller may processthe signal and transmit a signal to an actuator according to the resultsof the processing. The actuator may comprise a controllable valve forcontrolling the flow of carbon dioxide to contact the cement mix, e.g.,hydraulic cement mix.

In certain embodiments, the invention provides a method for producing acement mix, e.g., hydraulic cement mix comprising (i) contacting a firstportion of cement mix, e.g., hydraulic cement mix comprising a firstportion of water and hydraulic cement in a mixer while the cement mix,e.g., hydraulic cement mix is mixing; and (ii) adding a second portionof cement mix, e.g., hydraulic cement mix to the first portion. Incertain aspects of this embodiment, said contacting is achieved bydirecting a flow of carbon dioxide to the first portion of cement mix,e.g., hydraulic cement mix.

In certain embodiments, the invention provides a method of retrofittingan existing cement mix, e.g., hydraulic cement mixing apparatuscomprising a mixer, comprising operably connecting to the existingcement mix, e.g., hydraulic cement mixing apparatus a system forcontacting a cement mix, e.g., hydraulic cement mix within the mixerwith carbon dioxide during mixing of the cement mix, e.g., hydrauliccement mix. In certain aspects of this embodiment, the system to contactthe cement mix, e.g., hydraulic cement mix in the mixer with carbondioxide comprises a system to direct a flow of carbon dioxide to thecement mix, e.g., hydraulic cement mix during mixing of the cement mix,e.g., hydraulic cement mix. The method may also comprise operablyconnecting a source of carbon dioxide to a conduit for delivering thecarbon dioxide to the mixer. The method may also comprise operablyconnecting the conduit to the mixer. The system may comprise an actuatorfor modulating delivery of carbon dioxide from the source of carbondioxide through the conduit. The system may comprise a control systemfor controlling the actuator, operably connected to the actuator. Thecontrol system may comprises a timer and a transmitter for sending asignal to the actuator based on the timing of the timer. The method maycomprise connecting the actuator to an existing control system for thecement mix, e.g., hydraulic cement mixing apparatus. The method maycomprise modifying the existing control system to control the actuator.The actuator may be operably connected to or configured to be operablyconnected to the conduit, the mixer, a control system for the mixer, orto a source of carbon dioxide, or a combination thereof. The actuatormay control a valve so as to control delivery of carbon dioxide to themixer. The method may comprise adding to the existing cement mix, e.g.,hydraulic cement mixing apparatus one or more sensors operably connectedto, or configured to be operably connected to, a control system, formonitoring one or more characteristics of the cement mix, e.g.,hydraulic cement mix, a gas mixture in contact with the cement mix,e.g., hydraulic cement mix, a component of the cement mix, e.g.,hydraulic cement mixing apparatus, or a component exposed to the cementmix, e.g., hydraulic cement mix, for example, one or more sensors is asensor for monitoring carbon dioxide concentration of a gas or atemperature.

IV. Apparatus and Systems

In one aspect, the invention provides apparatus and systems. Theapparatus may include one or more of a conduit for supplying carbondioxide from a carbon dioxide source to a mixer, a source of carbondioxide, a mixer, one or more sensors, one or more controllers, one ormore actuators, all as described herein.

For example, in certain embodiments the invention provides an apparatusfor addition of carbon dioxide to a mixture comprising hydraulic cement,where the apparatus comprises a mixer for mixing the cement mix, e.g.,hydraulic cement mix, and a system for delivering carbon dioxide to thecement mix, e.g., hydraulic cement mix in the mixer during mixing. Incertain embodiments, the system for delivering carbon dioxide isconfigured to deliver carbon dioxide to the surface of the cement mix,e.g., hydraulic cement mix during mixing. The system may include acarbon dioxide source, a conduit operably connecting the source and themixer for delivery of carbon dioxide to the mixer, a metering system formetering flow of carbon dioxide in the conduit, and an adjustable valveto adjust the flow rate. In addition, the apparatus may include one ormore sensors to sense carbon dioxide content of gas in the mixer, oroutside the mixer. The apparatus may also include one or more sensorsfor sensing the temperature of the cement mix, e.g., hydraulic cementmix, or the mixer or other component. The apparatus may further includea controller that is operably connected to the one or more sensors,e.g., to one or more temperature sensors, one or more carbon dioxidesensors, or a combination thereof, and which is configured to receivedata from the one or more sensors. The controller may be configured todisplay the data, e.g., so that a human operator may adjust flow orother parameters based on the data. The controller may be configured toperform one or more operations on the data, and to send output to one ormore actuators based on the results of the one or more operations. Forexample, the controller may be configured to send output to a anadjustable valve causing it to modulate the flow of carbon dioxide inthe conduit, e.g., to stop the flow after a particular temperature, orcarbon dioxide concentration, or both, has been achieved.

In certain embodiments the invention provides a system for retrofittingan existing cement mix, e.g., hydraulic cement mix apparatus to allowcarbon dioxide to be contacted with a cement mix, e.g., hydraulic cementmix during mixing. The system may be configured to be transported from asite remote from the site of the existing cement mix, e.g., hydrauliccement mix apparatus to the site of the existing cement mix, e.g.,hydraulic cement mix apparatus.

In certain embodiments the invention provides an apparatus forcarbonating a cement mix comprising a cement binder and aggregate in acement mix apparatus during a mix operation, comprising (i) a mixer formixing the cement mix; (ii) a system for contacting the cement mix inthe mixer with carbon dioxide operably connected to the mixer andcomprising an actuator for modulating a flow of carbon dioxide to themixer; (iii) a sensor positioned and configured to monitor acharacteristic of the mix operation; and to transmit informationregarding the characteristic to a controller; (iv) the controller,wherein the controller is configured (e.g., programmed) to process theinformation and determine whether or not and/or to what degree tomodulate the flow of carbon dioxide to the mixer and to transmit asignal to the actuator to modulate the flow of carbon dioxide to themixer. In addition to, or instead of, the actuator for modulating a flowof carbon dioxide, the system may include one or more actuators formodulating another characteristic of the system, and the controller maybe configured to determine whether or not and to what degree to modulatethe other characteristic, and transmit a signal to the actuator formodulating the other characteristic.

The mixer may be any suitable mixer so long as it can be configured withthe remaining elements of the apparatus, such as mixers describedherein. In certain embodiments, the mixer is a stationery mixer, such asa mixer used in a precast operation. In certain embodiments, the mixeris a transportable mixer, such as the drum of a ready mix truck. Inembodiments in which the mixer is transportable, one or more of theelements of the control system for contacting the cement mix with carbondioxide, sensing a characteristic, controlling one or morecharacteristics such as carbon dioxide flow, and actuators, may beconfigured to be transported along with the mixer, or may be configuredto be detachable from the mixer, for example, to remain at a batchingstation for a ready mix truck. See, e.g. FIGS. 3 and 4, which showelements of the carbon dioxide delivery system in eithernon-transportable or transportable form. Elements of the control systemmay be similarly transportable or non-transportable. It will beappreciated that some parts of the system may be transported whileothers remain at, e.g. the batching station. For example, all carbondioxide may be delivered at the batching station but certaincharacteristics of the cement mix, e.g., rheology, may be monitoredwhile the truck in en route to the job site, and, if necessary, thecement mix may be modulated based on the monitoring, e.g., by additionof an admixture, or water, etc.

The system for contacting the cement mix in the mixer with carbondioxide may be any suitable system, such as the systems describedherein. In certain embodiments, the system is configured to delivergaseous carbon dioxide to the cement mix. In certain embodiments, thesystem is configured to deliver liquid carbon dioxide to the cement mixin such a manner that the liquid carbon dioxide is converted to gaseousand solid carbon dioxide as it is delivered to the cement mix, asdescribed herein. The system may be configured to deliver carbon dioxideto the surface of the mixing cement mix, or underneath the surface, or acombination thereof. In the case of a ready mix truck, the system forcontacting the cement in the mixer with carbon dioxide may share aconduit with the water delivery system, by means of a T junction in theconduit, such that either water or carbon dioxide can be delivered to afinal common conduit. See Examples 2 and 6.

The sensor may be any suitable sensor so long as it is configured andpositioned to transmit relevant information to the controller. Incertain embodiments, the characteristic of the mix operation that ismonitored by the sensor comprises a characteristic of the cement binder,the cement mix, a gas mixture in contact with the cement mix or themixer, or a component of the cement mix apparatus. In certainembodiments, the sensor is configured and positioned to monitor (a) massof cement binder added to the cement mix, (b) location of the cementbinder in the mix apparatus, (c) carbon dioxide content of a gas mixturewithin the mixer in contact with the cement mix, (d) carbon dioxidecontent of a gas mixture exiting from the mixer, (e) carbon dioxidecontent of gas mixture in the vicinity of the mix apparatus, (f)temperature of the cement mix or a component of the mix apparatus incontact with the cement mix, (g) rheology of the cement mix, (h)moisture content of the cement mix, or (i) pH of the cement mix. Incertain embodiments, the characteristic monitored by the sensorcomprises carbon dioxide content of a gas mixture exiting from themixer; this can be monitored by a single sensor or by a plurality ofsensors placed at various leak locations, in which case the controlleruses information from the plurality of sensors. The controller can beconfigured to send a signal to the actuator to modulate the flow ofcarbon dioxide when the carbon dioxide content of the gas mixturereaches a threshold value. Alternatively, or in addition, the controllercan be configured to send a signal to the actuator to modulate the flowof carbon dioxide when a rate of change of the carbon dioxide content ofthe gas mixture reaches a threshold value. In certain embodiments, thecharacteristic monitored by the sensor comprise the temperature of thecement mix or a component of the mix apparatus in contact with thecement mix. The controller can be configured to send a signal to theactuator to modulate the flow of carbon dioxide when the temperature ofthe cement mix or a component of the mix apparatus in contact with thecement mix reaches a threshold value. Alternatively, or in addition, thecontroller can be configured to send a signal to the actuator tomodulate the flow of carbon dioxide when a rate of change of thetemperature of the cement mix or a component of the mix apparatus incontact with the cement mix reaches a threshold value.

In certain embodiments, the apparatus comprises a plurality of sensorsconfigured to monitor a plurality of characteristics a plurality ofcharacteristics of the cement binder, the cement mix, a gas mixture incontact with the cement mix or the mixer, or a component of the cementmix apparatus e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, or 10characteristics, for example, at least 2 of (i) mass of cement binderadded to the cement mix, (ii) location of the cement binder in themixer, (iii) carbon dioxide content of a gas mixture within the mixer incontact with the cement mix, (iv) carbon dioxide content of gas mixtureexiting from the mixer, (v) carbon dioxide content of gas mixture in thevicinity of the mixer, (vi) temperature of the cement mix or a componentin contact with the cement mix, (vii) rheology of the cement mix, (viii)moisture content of the cement mix. In certain embodiments, a pluralityof sensors is configured and positioned to monitor at least 3 of (i)mass of cement binder added to the cement mix, (ii) location of thecement binder in the mixer, (iii) carbon dioxide content of a gasmixture within the mixer in contact with the cement mix, (iv) carbondioxide content of gas mixture exiting from the mixer, (v) carbondioxide content of gas mixture in the vicinity of the mixer, (vi)temperature of the cement mix or a component in contact with the cementmix, (vii) rheology of the cement mix, (viii) moisture content of thecement mix. In certain embodiments, a plurality of sensors is configuredand positioned to monitor at least 4 of (i) mass of cement binder addedto the cement mix, (ii) location of the cement binder in the mixer,(iii) carbon dioxide content of a gas mixture within the mixer incontact with the cement mix, (iv) carbon dioxide content of gas mixtureexiting from the mixer, (v) carbon dioxide content of gas mixture in thevicinity of the mixer, (vi) temperature of the cement mix or a componentin contact with the cement mix, (vii) rheology of the cement mix, (viii)moisture content of the cement mix. In certain embodiments, a pluralityof sensors is configured and positioned to monitor at least 5 of (i)mass of cement binder added to the cement mix, (ii) location of thecement binder in the mixer, (iii) carbon dioxide content of a gasmixture within the mixer in contact with the cement mix, (iv) carbondioxide content of gas mixture exiting from the mixer, (v) carbondioxide content of gas mixture in the vicinity of the mixer, (vi)temperature of the cement mix or a component in contact with the cementmix, (vii) rheology of the cement mix, (viii) moisture content of thecement mix. In certain embodiments, a plurality of sensors is configuredand positioned to monitor at least 6 of (i) mass of cement binder addedto the cement mix, (ii) location of the cement binder in the mixer,(iii) carbon dioxide content of a gas mixture within the mixer incontact with the cement mix, (iv) carbon dioxide content of gas mixtureexiting from the mixer, (v) carbon dioxide content of gas mixture in thevicinity of the mixer, (vi) temperature of the cement mix or a componentin contact with the cement mix, (vii) rheology of the cement mix, (viii)moisture content of the cement mix.

In addition to these sensors, or alternatively, the apparatus mayinclude one or more sensors to monitor the time of exposure of thecement mix to the carbon dioxide, the flow rate of the carbon dioxide,or both. For example, a sensor may signal when a valve to supply carbondioxide has opened, and, e.g., the flow rate of the carbon dioxide, anda timer circuit in the controller can determine total carbon dioxidedose.

Sensors may be wired to the controller or may transmit informationwirelessly, or any combination thereof.

The apparatus may additionally, or alternatively, include an actuatorconfigured to modulate an additional characteristic of the mixoperation, where the actuator is operably connected to the controllerand wherein the controller is configured to send a signal to theactuator to modulate the additional characteristic based on theprocessing of information from one or more sensors. This actuator can beconfigured to modulate addition of admixture to the cement mix, type ofadmixture added to the cement mix, timing of addition of admixture tothe cement mix, amount of admixture added to the cement mix, amount ofwater added to the cement mix, timing of addition of water to the cementmix, or cooling the cement mix during or after carbon dioxide addition.In certain embodiments, the apparatus comprises a plurality of suchactuators, such as at least 2, 3, 4, 5, 6, 7, or 8 such actuators.

The actuators may be wired to the controller, or may receive signalsfrom the controller wirelessly.

The controller may be any suitable controller so long as it is capableof being configured to receive information from one or more sensors,process the information to determine if an output is required, andtransmit signals to one or more actuators, as necessary, based on theprocessing; e.g., a computer. For example, the controller can be aProgrammable Logic Controller (PLC), optionally with a Human MachineInterface (HMI), as described elsewhere herein. The controller may belocated onsite with the mixer, or it may be remote, e.g., a physicalremote controller or a Cloud-based controller. In certain embodiments,the controller is configured to store and process the informationobtained regarding the characteristic monitored by the sensor for afirst batch of cement mix and to adjust conditions for a subsequentsecond cement mix batch based on the processing to optimize one or moreaspects of the mix operation. For example, the controller may adjust thesecond mix recipe, e.g., amount of water used or timing of wateraddition, or carbon dioxide exposure in the second batch to improvecarbon dioxide uptake, or to improve rheology or other characteristicsof the mix. In such embodiments in which one or more conditions of asecond mix operation are adjusted, in certain embodiments the one ormore conditions of the second mix operation includes (a) total amount ofcarbon dioxide added to the cement mix, (b) rate of addition of carbondioxide, (c) time of addition of carbon dioxide to the cement mix, (d)whether or not an admixture is added to the cement mix, (e) type ofadmixture added to the cement mix, (f) timing of addition of admixtureto the cement mix, (g) amount of admixture added to the cement mix, (h)amount of water added to the cement mix, (i) timing of addition of waterto the cement mix, (j) cooling the cement mix during or after carbondioxide addition, or a combination thereof. The controller can alsoreceive additional information regarding one or more characteristics ofthe cement mix measured after the cement mix leaves the mixer, andadjusts conditions for the second cement mix batch based on processingthat further comprises the additional information. In certainembodiments, the one or more characteristics of the cement mix measuredafter the cement mix leaves the mixer comprises (a) rheology of thecement mix at one or more time points, (b) strength of the cement mix atone or more time points, (c) shrinkage of the cement mix, (d) waterabsorption of the cement mix, or a combination thereof. Othercharacteristics include water content, carbon dioxide analysis toconfirm carbon dioxide uptake, calcite content (e.g., as determined byinfrared spectroscopy), elastic modulus, density, and permeability. Anyother suitable characteristic, as known in the art, may be measured.

In embodiments in which a controller adjusts conditions for a second mixoperation based on input from a first mix operation, the second mixoperation may be in the same mix facility or it may be in a differentmix facility. In certain embodiments, the controller, one or moresensors, one or more actuators, or combination thereof, transmitsinformation regarding the characteristics monitored and conditionsmodulated to a central controller that receives information from aplurality of controllers, sensors, actuators, or combination thereof,each of which transmits information from a separate mixer and mixoperation to the central controller. In these embodiments, the apparatusmay include a second controller that is the central controller, or thecentral controller may be the only controller for the apparatus. Thus,for example, a first mix facility may have a first sensor to monitor afirst characteristic of the first mix operation, and a second mixfacility may have a second sensor to monitor a second characteristic ofa second mix operation, and both may send information regarding thefirst and second characteristics to a central controller, whichprocesses the information and transmit a signal to the first, second, oreven a third, fourth, fifth, etc., mix operation to adjust conditionsbased on the first and second signals from the first and second sensors.Additional information that will be typically transmitted to the centralcontroller includes mix components for the mixes at the first and secondmix operations (e.g., type and amount of cement binder, amount of waterand w/c ratio, types and amounts of aggregate, whether aggregate was wetor dry, admixtures, and the like) amount, rate, and timing of carbondioxide addition, and any other characteristic of the first and secondmix operations that would be useful for determining conditions tomodulate future mix operations based on the characteristics achieved inpast mix operations. Any number of mix operations may input informationto the central controller, e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, or 10mix operations, or at least 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, or100 mix operations. The central controller may also receive any otherinformation that may be suitable to informing decisions regarding mixoperations to optimize one or more conditions of the mix operationand/or of the cement mix produced in the operation. For example, thecentral controller may receive information from experiments conductedwith various types of cements (e.g., various types of Portland cements)carbonated under various conditions, and/or exposed to variousadmixtures, such as at different times, or in different concentrations,and the like, and the resulting characteristics of the cement mix, suchas rheology at one or more timepoints, strength at one or moretimepoints, and the like. Any other suitable information, such asinformation published in literature, or obtained in any manner, may beinput into the central controller, e.g., automatically and/or through aHuman Machine Interface. The information the central controller receivescan be processed and used to adjust cement mix operations at any mixoperation to which the central controller can transmit outputs. Thus,the central controller can learn from numerous mix operations tooptimize future operations and, over time, can accumulate a database toinform decisions in mix operations at a mix site even if a particularmix recipe and/or conditions have never been used at that site, or evenpredict optimum conditions for a mix recipe that has not been used atany of the sites to which the controller is connected. The centralcontroller can match to past mix recipes, or predict optimum conditionsfor a new mix recipe based on suitable algorithms using information inits database, or both.

In certain embodiments in which the controller adjust as a second mixoperation based on characteristics monitored in a first mix operation,the one or more characteristics of the mix operation may comprise totalamount of carbon dioxide added to the cement mix, rate of addition ofcarbon dioxide, time of addition of carbon dioxide to the cement mix,whether or not an admixture is added to the cement mix, type ofadmixture added to the cement mix, timing of addition of admixture tothe cement mix, amount of admixture added to the cement mix, amount ofwater added to the cement mix, timing of addition of water to the cementmix, cooling the cement mix during or after carbon dioxide addition, ora combination thereof.

The controller can be further configured, e.g., programmed, to receiveand process information regarding one or more characteristics of thecement mix measured after the cement mix leaves the mixer, and totransmit signals to one or more actuators configured to adjustconditions for the second cement mix batch based on the processing toimprove contact with the carbon dioxide or another characteristic of themix operation in the second mix operation. The one or morecharacteristics of the cement mix measured after the cement mix leavesthe mixer can be rheology of the cement mix at one or more time points,strength of the cement mix at one or more time points, water absorption,shrinkage, and the like. The characteristic monitored can depend on therequirements for a particular mix batch, although other characteristicsmay also be monitored to provide data to the controller for futurebatches in which those characteristics would be required.

The use of an apparatus that includes a control system, whether for asingle mix operation or for a plurality of mix operations, can producevery high efficiencies of carbon dioxide uptake (ratio of carbon dioxideor carbon dioxide derivatives in the cement mix to total carbon dioxidedelivered). In certain embodiments, the apparatus is configured tocontrol one or more actuators such that an efficiency of carbonation ofat least 60, 70, 80, 90, 95, 96, 97, 98, 99, or 99.5% is achieved. Suchhigh efficiencies allow for greater sequestration of greenhouse gaswithout leakage into the atmosphere, as well as a more economicaloperation.

In certain embodiments, the invention provides a controller forcontrolling a cement mix mixing operation comprising carbonation of thecement mix in a mixer by exposing the cement mix to carbon dioxide,where the controller comprises (i) an input port for receiving a signalfrom a sensor that monitors a characteristic of the cement mix mixingoperation; (ii) a processor for processing the signal from the sensorand formulating an output signal to modulate the exposure of the cementmix to carbon dioxide or to modulate a characteristic of the cement mix;and (iii) an output port for transmitting the output signal to anactuator that modulates the exposure of the cement mix to carbon dioxideor that modulates a characteristic of the cement mix. The input andoutput ports may be configured to be wired to the sensor or actuator, orto receive a wireless signal, or a combination of such ports may beused. In certain embodiments, the input port is configured to receive aplurality of signals from a plurality of sensors, and the processor isconfigured to process the plurality of signals and formulate an outputsignal to modulate the exposure of the cement mix to carbon dioxide orto modulate a characteristic of the cement mix. Thus, the input port mayinclude a plurality separate ports that are wired to various sensors, ora wireless port that is configured to receive signals from a pluralityof sensors, or a combination of one or more wired and wireless ports forone or more sensors. The controller can be is configured to formulate aplurality of output signals to modulate the exposure of the cement mixto carbon dioxide or to modulate a characteristic of the cement mix andthe output port is configured to transmit the plurality of signals.Similar to an input port for a plurality of signals, this can be a wiredoutput port with a plurality of ports, a wireless port configured tosend a plurality of signals, or a combination of wired and wirelessports to send one or more signals each.

The controller may be configured to process any signal from any suitablesensor, such as described herein, and to send output to any suitableactuator, such as described herein. The controller may also beconfigured to send information to a central controller, or may itself bea central controller that is configured to receive input from, and sendoutput to, a plurality of mix operations, also as described herein.

In certain embodiments, the invention provides a network comprising aplurality of spatially separate cement mix operations, such as at least2, 3, 4, 5, 6, 7, 8, 9, or 10, or at least 20, 30, 40, 50, 70, or 100separate mix operations, each of which comprises at least one sensor formonitoring at least one characteristic of its operation, and comprisinga central processing unit, to which each sensor sends its informationand which stores and/or processes the information. Alternatively, or inaddition, information regarding at least one characteristic of the mixoperation may be input manually into the central processing unit, e.g.,through a HMI. One or more of the mix operations may be a mix operationin which the cement mix is carbonated, e.g., as described herein, suchas a mix operation in which the cement is carbonated, i.e., exposed tocarbon dioxide in such a way that the carbon dioxide is taken up by thecement mix, during mixing. The mix operations may also include sensorsor other means by which one or more characteristics of the cement mix ismonitored, before, during, or after mixing, e.g., also as describedherein, which transmit information to the central processor. The centralprocessor may also be configured to output signals to one or more of themix operations, or to other mix operations, based on the processing ofthe signals.

In certain embodiments, the invention provides an apparatus forproducing a cement mix, e.g., hydraulic cement mix comprising (i) amixer for mixing a cement mix, e.g., hydraulic cement mix; and (ii) asystem for exposing the cement mix, e.g., hydraulic cement mix to carbondioxide during mixing, wherein the system is configured to delivercarbon dioxide to the surface of the cement mix, e.g., hydraulic cementmix.

In certain embodiments, the invention provides an apparatus for mixing acement mix, e.g., hydraulic cement mix comprising (i) a mixer for mixingthe cement mix, e.g., hydraulic cement mix; (ii) a system for contactingthe cement mix, e.g., hydraulic cement mix with carbon dioxide directedto the cement mix, e.g., hydraulic cement mix operably connected to themixer; (iii) a sensor positioned and configured to monitor one or morecharacteristics of the cement mix, e.g., hydraulic cement mix, a gasmixture in contact with the cement mix, e.g., hydraulic cement mix, acomponent of a cement mix, e.g., hydraulic cement mix apparatus, or acomponent exposed to the cement mix, e.g., hydraulic cement mix; and(iv) an actuator operably connected to the sensor for modulating theflow of the carbon dioxide based on the characteristic monitored. Incertain aspects of this embodiment, the system for contacting the cementmix, e.g., hydraulic cement mix with carbon dioxide comprises a system asystem for contacting the cement mix, e.g., hydraulic cement mix with aflow of carbon dioxide directed to the cement mix, e.g., hydrauliccement mix.

In certain embodiments, the invention provides an apparatus forretrofitting an existing cement mix, e.g., hydraulic cement mixercomprising a conduit configured to be operably connected to a source ofcarbon dioxide and to the mixer, for delivering carbon dioxide from thesource to the mixer. The apparatus may comprise the source of carbondioxide. The apparatus may comprise an actuator for controlling deliveryof carbon dioxide from a source of carbon dioxide through the conduit,wherein the actuator is operably connected or is configured to beoperably connected to a control system. The apparatus may furthercomprise the control system. The control system may comprise a timer anda transmitter for sending a signal to the actuator based on the timingof the timer. The control system may be an existing control system forthe mixer. The apparatus may comprise instructions for modifying theexisting control system to control the actuator. The actuator may beoperably connected to or configured to be operably connected to theconduit, the mixer, a control system for the mixer, or to a source ofcarbon dioxide, or a combination thereof. The actuator may control avalve so as to control delivery of carbon dioxide to the mixer. Theapparatus may comprise one or more sensors operably connected to, orconfigured to be operably connected to, the control system formonitoring one or more characteristics of the cement mix, e.g.,hydraulic cement mix, a gas mixture adjacent to the cement mix, e.g.,hydraulic cement mix, or a component in contact with the cement mix,e.g., hydraulic cement mix. The one or more sensors may be a sensor formonitoring carbon dioxide concentration of a gas or a temperature.

In certain embodiments, the invention provides a system for exposing acement mix, e.g., hydraulic cement mix within a transportable mixer tocarbon dioxide comprising (i) a source of carbon dioxide that is morethan 50% pure carbon dioxide; (ii) a transportable mixer for mixing acement mix, e.g., hydraulic cement mix; and (iii) a conduit operablyconnected to the source of carbon dioxide and to the mixer fordelivering carbon dioxide from the source of carbon dioxide to thecement mix, e.g., hydraulic cement mix. The system may further comprisean an actuator operably connected to the conduit for controlling theflow of the carbon dioxide. The actuator may comprise a valve. Thesystem may comprise a controller operably connected to the actuator,where the controller is configured to operate the actuator based onpredetermined parameters, on feedback from one or more sensors, or acombination thereof. In certain embodiments the source of carbon dioxideand the conduit are housed in a portable unit that can be moved from onereadymix site to another, to provide carbon dioxide to more than onereadymix truck.

In certain embodiments, the invention provides a system for exposing acement mix, e.g., hydraulic cement mix within a mixer to carbon dioxidecomprising (i) a source of carbon dioxide; (ii) the mixer for mixing thecement mix, e.g., hydraulic cement mix; (iii) a conduit operablyconnected to the source of carbon dioxide and to the mixer fordelivering carbon dioxide from the source of carbon dioxide to thecement mix, e.g., hydraulic cement mix; (iv) a sensor positioned andconfigured to monitor one or more one or more characteristics of thecement mix, e.g., hydraulic cement mix, a gas mixture adjacent to thecement mix, e.g., hydraulic cement mix, or a component in contact withthe cement mix, e.g., hydraulic cement mix; and (v) an actuator operablyconnected to the sensor and to the system for exposing the cement mix,e.g., hydraulic cement mix to carbon dioxide, wherein the actuator isconfigured to alter the exposure of the cement mix, e.g., hydrauliccement mix to the carbon dioxide based on the characteristic monitoredby the sensor. The mixer may be a stationary mixer. The mixer may be atransportable mixer.

V. Compositions

The invention also provides compositions, e.g., compositions that may beproduced by the methods described herein. In certain embodiment theconcrete mix is fluid, that is, capable of being mixed in the mixer andpoured for its intended purpose. In certain embodiments the inventionprovides a composition that is a dry carbonated concrete mix that isfluid and compactable, e.g., sufficiently fluid and compactable to beplaced in a mold for a pre-cast concrete product, that compriseshydraulic cement, e.g., OPC, and carbon dioxide and/or reaction productsof carbon dioxide with the OPC and/or other components of the mix, and,optionally, one or more of aggregates and an admixture, such as anadmixture to modulate the compactability of the carbonated concrete mix,and/or a strength accelerator. In certain embodiments the admixturecomprises a set retarder, such as a sugar or sugar derivative, e.g.,sodium gluconate. In certain embodiments the invention provides acomposition that is a wet carbonated concrete mix that is fluid andpourable, e.g., sufficiently fluid and pourable to be poured in a moldat a construction site, that comprises hydraulic cement, e.g., OPC, andcarbon dioxide and/or reaction products of carbon dioxide with the OPCand/or other components of the mix, and, optionally, one or more ofaggregates and an admixture, such as an admixture to modulate theflowability of the carbonated concrete mix, and/or a strengthaccelerator. In certain embodiments the admixture comprises a setretarder, such as a sugar or sugar derivative, e.g., sodium gluconate.

In some methods, solid carbon dioxide (dry ice) is added to the cementmix, producing a composition comprising a cement mix, such as ahydraulic cement mix such as concrete, and solid carbon dioxide. Thesolid carbon dioxide may be present in an amount of greater than 0.01,0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3,1.4, 1.5, 1.7, 2.0, or 2.5% bwc, or 0.01-5%, 0.01-2%, 0.01-1%,0.01-0.5%, 0.1-5%, 0.1-2%, 0.1-1%, or 0.1-0.5%. In certain embodimentsthe invention provides a cement mix comprising gaseous carbon dioxide orcarbon dioxide reaction products, such as carbonates, and solid carbondioxide. The solid carbon dioxide may be present in an amount of greaterthan 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1,1.2, 1.3, 1.4, 1.5, 1.7, 2.0, or 2.5% bwc or 0.01-5%, 0.01-2%, 0.01-1%,0.01-0.5%, 0.1-5%, 0.1-2%, 0.1-1%, or 0.1-0.5%. The gaseous carbondioxide or carbon dioxide reaction products may be present in an amountof greater than 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9,1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.7, 2.0, or 2.5% bwc, or 0.01-5%,0.01-2%, 0.01-1%, 0.01-0.5%, 0.1-5%, 0.1-2%, 0.1-1%, or 0.1-0.5%. Carbondioxide reaction products include carbonic acid, bicarbonate, and allforms of calcium carbonate (e.g., amorphous calcium carbonate, vaterite,aragonite, and calcite), as well as other products formed by thereaction of carbon dioxide with various components of the cement mix.The solid carbon dioxide may be added as a single block, or more thanone block, such as more than 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 50, or 100blocks. In some embodiments, the solid carbon dioxide is formed fromrelease of liquid carbon dioxide into the mix.

The cement mix may contain an admixture, such as any admixture asdescribed herein, e.g., a carbohydrate or carbohydrate derivative, suchas sodium gluconate. The admixture may be present in an amount ofgreater than 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9,1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.7, 2.0, or 2.5%; or greater than 0.01,0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3,1.4, 1.5, 1.7, 2.0, or 2.5% and less than 0.05, 0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.7, 2.0, 2.5 or 3.0%,e.g., any range that may be expressed as the greater than and less thanamounts. Exemplary ranges include 0.01-3.0%, 0.01-1.5%, 0.01-1%,0.01-0.5%, 0.01-0.4%, 0.01-0.2%, 0.01-0.1%, 0.1-3.0%, 0.1-1.5%, 0.1-1%,0.1-0.5%, 0.1-0.4%, 0.1-0.2%, or 0.1-0.1%.

It has been found that the addition of carbon dioxide to a cement mixduring mixing results in the formation of nanocrystals of calciumcarbonate. Earlier work has shown that adding exogenous nanocrystallinecalcium carbonate (e.g., calcium carbonate with a particle size in arange of 50-120 nm) to a concrete mix improved the hydration of the mix;however, when exogneously supplied calcium carbonate is used, a largequantity, such as 10% bwc, is needed to achieve the desired effect,probably due to clumping of the added nanocrystals. In contrast, in thepresent invention the calcium carbonate nanocrystals are formed in situ,without clumping, and thus a much greater dispersion is achieved. Forexample, the incidence of discrete single nanocrystals of less that 500nm, or less than 400 nm, or less than 300 nm, or less than 200 nmparticle size in compositions of the invention may be over 10, 20, 30,40, 50, 60, or 80% of the calcium carbonate in the composition. Ascrystal formation starts, crystal size for at least 10, 20, 30, 40, or50% of the calcium carbonate in the composition may be less 100, 80, 60,50, 40, or 30 nm. In addition, the polymorphic composition of thecrystals may vary, depending on the time the composition has beenreacting, the timing of addition of carbon dioxide, the use ofcrystal-modifying admixtures, and the like. In certain embodiments, atleast 1, 5, 10, 20, 30, 40, or 50% of the calcium carbonate in thecomposition is amorphous calcium carbonate, or 0.01-50%, 0.1-50%, 1-50%,5-50%, 10-50%, or 20-50%. In certain embodiments, at least 1, 5, 10, 20,30, 40, or 50% of the calcium carbonate in the composition is vaterite,0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or 20-50%. In certainembodiments, at least 1, 5, 10, 20, 30, 40, or 50% of the calciumcarbonate in the composition is aragonite, 0.01-50%, 0.1-50%, 1-50%,5-50%, 10-50%, or 20-50%. In certain embodiments, at least 1, 5, 10, 20,30, 40, or 50% of the calcium carbonate in the composition is calcite,or 0.01-99.9%, 0.1-99.9%, 1-99%, 5-99.9%, 10-99.9%, 30-99.9%, 50-99.9%,0.01-90%, 0.1-90%, 1-90%, 5-90%, 10-90%, 30-90%, 50-90%, 0.01-80%,0.1-80%, 1-80%, 5-80%, 10-80%, 30-80%, 50-80%. Any combination ofamorphous calcium carbonate, vaterite, aragonite, and/or calcite mayalso be present, for example at the indicated percentages.

Compositions of the invention may also include one or more supplementarycementitious materials (SCMs) and/or cement replacements, as describedelsewhere herein. In certain embodiments, a compositin of the inventionincludes, in addition to cement, one or more SCMS and/or cementreplacements, for example blast furnace slag, fly ash, silica fume,natural pozzolans (such as metakaolin, calcined shale, calcined clay,volcanic glass, zeolitic trass or tuffs, rice husk ash, diatomaceousearth, and calcined shale), waste glass, limestone, recycled/wasteplastic, scrap tires, municipal solid waste ash, wood ash, cement kilndust, or foundry sand, at a suitable percentage of the composition bwc,such as 0.1-50%, or 1-50%, or 5-50%, or 10-50%, or 20-50%, or 1-40%, or5-40%, or 10-50%, or 20-40% bwc. In certain embodiments, the compositionincludes an SCM and in some of these embodiments the SCM is fly ash,slag, silica fume, or a naturual pozzolan. In certain embodiment, theSCM is fly ash. In certain embodiments, the SCM is slag.

Thus, in certain embodiments, the invention provides a fluid cement mix,e.g., hydraulic cement mix composition comprising (i) a wet cement mix,e.g., hydraulic cement mix comprising hydraulic cement and water in aw/c ratio of no more than 0.4, or 0.3, or 0.2 and (ii) carbon dioxide orcarbonation product in an amount of at least 0.05% by weight of cement(bwc). The composition is in a mixable and/or flowable state, e.g., setand hardening have not progressed to the point where the mixture can nolonger be mixed by the apparatus in which it is formed. The compositionmay further comprise (ii) an admixture for modulating the flowability ofthe cement mix, e.g., hydraulic cement mixture. The admixture may apolycarboxylate superplasticer, a naphthalene HRWR, or a combinationthereof.

In certain embodiments, the invention provides a fluid cement mix, e.g.,hydraulic cement mix composition comprising (i) a wet cement mix, e.g.,hydraulic cement mix comprising hydraulic cement and water; (ii) carbondioxide or carbonation product in an amount of at least 0.05% bwc; (iii)an admixture for modulating the flowability of the wet hydraulic cementmix. In certain embodiments the admixture comprises a polycarboxylatesuperplasticer, a naphthalene HRWR, or any combination thereof.

In certain embodiments, the invention provides a cement mix, e.g.,hydraulic cement mix composition, which may be a fluid cement mix,comprising (i) a wet cement mix, e.g., hydraulic cement mix comprisinghydraulic cement and water; (ii) carbon dioxide in solid, liquid, and/orgaseous form, or in aqueous solution as carbonic acid or bicarbonate, inan amount of 0.01-2% bwc; (iii) solid calcium carbonate in an amount of0.01-2% bwc; and (iii) a supplementary cementitious material and/orcement replacement. In certain embodiments, the carbon dioxide comprisescarbon dioxide in solid form. During mixing and later set and hardening,various intermediate compositions are produced, so that initialcompositions may contain mostly carbon dioxide in gasesous, liquid,solid form or in solution with little calcium carbonate formation, andlater compositions may contain mostly calcium carbonate with littlecarbon dioxide in gasesous, liquid, solid form or in solution. Incertain embodiments, the SCM and/or cement replacement comprises0.1-50%, or 1-50%, or 5-50%, or 10-50%, or 20-50%, or 1-40%, or 5-40%,or 10-50%, or 20-40% bwc in the composition. In certain embodiments, theSCM and/or cement replacement is blast furnace slag, fly ash, silicafume, natural pozzolans (such as metakaolin, calcined shale, calcinedclay, volcanic glass, zeolitic trass or tuffs, rice husk ash,diatomaceous earth, and calcined shale), limestone, waste glass,recycled/waste plastic, scrap tires, municipal solid waste ash, woodash, cement kiln dust, or foundry sand, or a combination thereof. Incertain embodiments, an SCM is used and in certain of these embodiments,the SCM is blast furnace slag, fly ash, silica fume, or naturalpozzolan, or a combination thereof. In certain embodiments, the SCM isblast furnace slag. In certain embodiments, the SCM is fly ash. Incertain embodiments, the SCM is silica fume. In certain embodiments, theSCM is a natural pozzolan. In certain embodiments the hydraulic cementis Portland cement. The composition may further comprise an admixture.In certain embodiments, the admixture is a carbohydrate or carbohydratederivative, such as sodium gluconate. The admixture may be present atany suitable concentration, such as 0.01-2%, or 0.01-1%, or 0.01-0.5%,or 0.01-0.4%, or 0.01-0.3%, or 0.01-0.2%, or 0.01-0.1%. The polymophiccomposition of the calcium carbonate may include any of the polymorphsdescribed herein. In certain embodiments, at least 1, 5, 10, 20, 30, 40,or 50% of the calcium carbonate in the composition is amorphous calciumcarbonate, or 0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or 20-50%. Incertain embodiments, at least 1, 5, 10, 20, 30, 40, or 50% of thecalcium carbonate in the composition is vaterite, or 0.01-50%, 0.1-50%,1-50%, 5-50%, 10-50%, or 20-50%. In certain embodiments, at least 1, 5,10, 20, 30, 40, or 50% of the calcium carbonate in the composition isaragonite, or 0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or 20-50%. Incertain embodiments, at least 1, 5, 10, 20, 30, 40, or 50% of thecalcium carbonate in the composition is calcite, or 0.01-99.9%,0.1-99.9%, 1-99%, 5-99.9%, 10-99.9%, 30-99.9%, 50-99.9%, 0.01-90%,0.1-90%, 1-90%, 5-90%, 10-90%, 30-90%, 50-90%, 0.01-80%, 0.1-80%, 1-80%,5-80%, 10-80%, 30-80%, 50-80%. Any combination of amorphous calciumcarbonate, vaterite, aragonite, and/or calcite may also be present, forexample at the indicated percentages.

In certain embodiments, the invention provides a set or hardened cementmix, e.g., hydraulic cement mix composition such as a set or hardenedconcrete, comprising (i) reaction products formed in a wet cement mix,e.g., hydraulic cement mix comprising hydraulic cement and water, suchas reaction products of a Portland cement mix; (iii) calcium carbonatein an amount of 0.01-5% bwc, or 0.01-2% bwc, where the calciuumcarbonate is present as crystals or particles wherein at least 10, 20,50, 70, or 90% of the particles are less than 1 μm, or less than 500 nm,or less than 400 nm, or less than 200 nm in average dimension; and (iii)a supplementary cementitious material and/or cement replacement and/orreaction products of supplmentary cementitious material or cementreplacement. In certain embodiments, the SCM and/or cement replacementcomprises 0.1-50%, or 1-50%, or 5-50%, or 10-50%, or 20-50%, or 1-40%,or 5-40%, or 10-50%, or 20-40% bwc in the composition. In certainembodiments, the SCM and/or cement replacement is blast furnace slag,fly ash, silica fume, natural pozzolans (such as metakaolin, calcinedshale, calcined clay, volcanic glass, zeolitic trass or tuffs, rice huskash, diatomaceous earth, and calcined shale), limestone, waste glass,recycled/waste plastic, scrap tires, municipal solid waste ash, woodash, cement kiln dust, or foundry sand, or a combination thereof. Incertain embodiments, an SCM is used and in certain embodiments, the SCMis blast furnace slag, fly ash, silica fume, or natural pozzolan, or acombination thereof. In certain embodiments, the SCM is blast furnaceslag. In certain embodiment, the SCM is fly ash. In certain embodiments,the SCM is silica fume. In certain embodiments, the SCM is a naturalpozzolan. In certain embodiments the hydraulic cement or reactionproducts is Portland cement or Portland cement reaction products. Thecomposition may further comprise an admixture. In certain embodiments,the admixture is a carbohydrate or carbohydrate derivative, such assodium gluconate. The admixture may be present at any suitableconcentration, such as 0.01-2%, or 0.01-1%, or 0.01-0.5%, or 0.01-0.4%,or 0.01-0.3%, or 0.01-0.2%, or 0.01-0.1%. The polymophic composition ofthe calcium carbonate may include any of the polymorphs describedherein. In certain embodiments, at least 1, 5, 10, 20, 30, 40, or 50% ofthe calcium carbonate in the composition is amorphous calcium carbonate,or 0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or 20-50%. In certainembodiments, at least 1, 5, 10, 20, 30, 40, or 50% of the calciumcarbonate in the composition is vaterite, or 0.01-50%, 0.1-50%, 1-50%,5-50%, 10-50%, or 20-50%. In certain embodiments, at least 1, 5, 10, 20,30, 40, or 50% of the calcium carbonate in the composition is aragonite,or 0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or 20-50%. In certainembodiments, at least 1, 5, 10, 20, 30, 40, or 50% of the calciumcarbonate in the composition is calcite, or 0.01-99.9%, 0.1-99.9%,1-99%, 5-99.9%, 10-99.9%, 30-99.9%, 50-99.9%, 0.01-90%, 0.1-90%, 1-90%,5-90%, 10-90%, 30-90%, 50-90%, 0.01-80%, 0.1-80%, 1-80%, 5-80%, 10-80%,30-80%, 50-80%. Any combination of amorphous calcium carbonate,vaterite, aragonite, and/or calcite may also be present, for example atthe indicated percentages.

In certain embodiments, the invention provides a cement mix, e.g.,hydraulic cement mix composition, which may be a fluid cement mix,comprising (i) a wet cement mix, e.g., hydraulic cement mix comprisinghydraulic cement and water; (ii) calcium carbonate that isnanocrystalline where the incidence of discrete single nanocrystals ofless that 500 nm, or less than 400 nm, or less than 300 nm, or less than200 nm, or less than 100 nm, or less than 50 nm particle size is over10, 20, 30, 40, 50, 60, or 80% of the calcium carbonate; and (iii) asupplementary cementitious material and/or cement replacement. It willbe appreciated that the nanocrystalline character of the composition asa whole may be determined by assaying the nanocrystalline character ofone or more representative samples. In certain embodiments, thenanocrystalline calcium carbonate comprises 0.01-5%, or 0.01-2%, or0.01-1%, or 0.01-0.5%, or 0.01-0.4%, or 0.01-0.3%, or 0.01-0.02%, or0.01-0.1% of the composition bwc. In certain embodiments, the SCM and/orcement replacement comprises 0.1-50%, or 1-50%, or 5-50%, or 10-50%, or20-50%, or 1-40%, or 5-40%, or 10-50%, or 20-40% bwc. In certainembodiments, the SCM and/or cement replacement is blast furnace slag,fly ash, silica fume, natural pozzolans (such as metakaolin, calcinedshale, calcined clay, volcanic glass, zeolitic trass or tuffs, rice huskash, diatomaceous earth, and calcined shale), limestone, waste glass,recycled/waste plastic, scrap tires, municipal solid waste ash, woodash, cement kiln dust, or foundry sand, or a combination thereof. Incertain embodiments, an SCM is used and in certain of these embodiments,the SCM is blast furnace slag, fly ash, silica fume, or naturalpozzolan, or a combination thereof. In certain embodiments, the SCM isblast furnace slag. In certain embodiment, the SCM is fly ash. Incertain embodiments, the SCM is silica fume. In certain embodiments, theSCM is a natural pozzolan. In certain embodiments the hydraulic cementis Portland cement. The composition may further comprise an admixture.In certain embodiments, the admixture is a carbohydrate or carbohydratederivative, such as sodium gluconate. The admixture may be present atany suitable concentration, such as 0.01-2%, or 0.01-1%, or 0.01-0.5%,or 0.01-0.4%, or 0.01-0.3%, or 0.01-0.2%, or 0.01-0.1%. The polymophiccomposition of the nanocrystals may include any of the polymorphsdescribed herein. In certain embodiments, at least 1, 5, 10, 20, 30, 40,or 50% of the calcium carbonate nanocrystals in the composition isamorphous calcium carbonate nanocrystals, or 0.01-50%, 0.1-50%, 1-50%,5-50%, 10-50%, or 20-50%. In certain embodiments, at least 1, 5, 10, 20,30, 40, or 50% of the calcium carbonate nanocrystals in the compositionis vaterite nanocrystals, or 0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or20-50%. In certain embodiments, at least 1, 5, 10, 20, 30, 40, or 50% ofthe calcium carbonate nanocrystals in the composition is aragonitenanocrystals, 0.01-50%, 0.1-50%, 1-50%, 5-50%, 10-50%, or 20-50%. Incertain embodiments, at least 1, 5, 10, 20, 30, 40, or 50% of thecalcium carbonate nanocrystals in the composition is calcitenanocrystals, or 0.01-99.9%, 0.1-99.9%, 1-99%, 5-99.9%, 10-99.9%,30-99.9%, 50-99.9%, 0.01-90%, 0.1-90%, 1-90%, 5-90%, 10-90%, 30-90%,50-90%, 0.01-80%, 0.1-80%, 1-80%, 5-80%, 10-80%, 30-80%, 50-80%. Anycombination of amorphous calcium carbonate, vaterite, aragonite, and/orcalcite may also be present, for example at the indicated percentages.It will be appreciated that the polymorphic makeup of the composition asa whole may be estimated by the polymorphic makeup of one or morerepresentative samples of the composition.

EXAMPLES Example 1

This example describes contacting a wet hydraulic cement mix (concrete)with carbon dioxide during mixing of the concrete.

A series of tests were conducted to contact wet concrete mix with carbondioxide during mixing of the concrete.

In a first experiment, bagged readymix concrete (Quikrete or Shaw), 20kg was mixed with water in a Hobart mixer. The cement content of theconcrete was not known but was assumed to be 12-14%. A value of 14% wasused in subsequent calculations. 0.957 kg of water, which was 57% of thefinal water, was added for a w/c ratio of 0.34 and the mixer was toppedwith a loose lid. The concrete mix was mixed for 1 minute. Then a gasmixture containing carbon dioxide at a concentration of 99.5%(Commercial grade carbon dioxide from Air Liquide, 99.5% CO2, UN1013,CAS:124-38-9) was delivered to contact the surface of the mixingconcrete via a tube of approximately ¼″ ID whose opening was locatedapproximately 10 cm from the surface of the mixing concrete, at a flowrate of 20 liters per minute (LPM) for 40-80 sec, for a total amount ofcarbon dioxide of 13.3 L (40 sec) to 26.7 L (80 sec). The remainingwater, 0.713 kg, was added to bring the mix to a w/c ratio of 0.6 whilethe concrete mix continued to be mixed after the carbon dioxide additionfor approximately 2 minutes, for a total mix time of approximately 4minutes, with carbon dioxide addition for 40, 60, or 80 sec during themixing. In general, the mixing procedure was as follows: mix dry mix andadd first water addition over 15 seconds; mix for remainder of oneminute; deliver CO₂ while mixing for 40, 60 or 80 seconds; when thedelivery was 40 seconds there was an additional 20 sec of post-CO₂mixing to bring the step up to one minute, when the delivery was 60 or80 seconds the next step began immediately after the CO₂ was stopped;add the second water addition and mix two minutes. In one test anadditional 5% water was added. These tests were done with Shaw prebagged mix, which required more water and was assumed to contain morecement (17%). The two water additions were 1.15 kg (58% giving 0.34estimated w/c) and 0.850 kg (to give a total of 2.0 kg of water andestimated 0.59 w/c). In the case of 5% added water it was only appliedon the second addition (1.150 kg or 55%, then 0.950 kg for a total of2.1 kg and estimated 0.62 w/c). Control concrete mixes were preparedwith the same final w/c ratio and mixing time, but no addition of carbondioxide. The mixed concrete was poured into cylinders and strength testswere performed at 7 days. The results are shown in FIGS. 4 and 5, wherethe bars represent the data range (high to low) and the point in themiddle corresponds to the average. The concrete mixes that had beenexposed to carbon dioxide showed 7-day strengths comparable to thecontrols.

In a second experiment, several batches were prepared. In each batch,approximately 20 kg of bagged readymix concrete (BOMIX bagged readymix)was mixed with water in a Hobart mixer. The cement content of theconcrete was not known but was assumed to be 20%. A first water additionof 0.6 kg (30% of total water) was added for a w/c ratio of 0.15 and themixer was topped with a loose lid. The concrete mix was mixed for atotal of 1 minute. Then a gas mixture containing carbon dioxide at aconcentration of 99.5% (Commercial grade carbon dioxide from AirLiquide, 99.5% CO2, UN1013, CAS:124-38-9) was delivered to contact thesurface of the mixing concrete via a tube of approximately ¼″ ID whoseopening was located approximately 10 cm from the surface of the mixingconcrete, at various flow rates for different batches, for 60 sec, togive different total carbon dioxide doses for different batches. Theremaining water of 1.4 kg was added to bring the mix to a w/c ratio of0.5 while the concrete mix continued to be mixed after the carbondioxide addition for approximately 2 minutes, for a total mix time ofapproximately 4 minutes, with carbon dioxide addition for 60 sec duringthe mixing (one minute premix, 60 sec CO₂ dose, then add remainder ofwater and finish with two minutes mixing for 4 minutes total). Controlconcrete mixes were prepared with the same final w/c ratio and mixingtime, but no addition of carbon dioxide. The mixed concrete was pouredinto 5 4 kg cylinders (100 mm diameter by 200 mm, or 4 inches by 8inches) and strength tests were performed at 7, 14, and 28 days. Thecarbon dioxide dosage is expressed on a per-cylinder basis, and was 5,10, 15, 20, 25, or 30 g per cylinder, depending on the batch, which was0.6, 1.3, 1.9, 2.5, 3.1, or 3.8% carbon dioxide bwc, respectively. Theresults are shown in FIGS. 6, 7, and 8. The concrete mixes that had beenexposed to carbon dioxide showed 7-day compressive strengths comparableto the controls, with a trend toward increasing 7-day strength withincreasing carbon dioxide dose (FIG. 6). 14-day compressive strengthswere comparable to or lower than controls at two doses, 15 and 20 g(FIG. 7). 28-day compressive strengths were comparable to the control,with a trend toward increasing 28-day strength with increasing carbondioxide dose (FIG. 8).

In a third experiment, additional water was added to compensate forreduced flowability (slump) observed in the concrete mixes contactedwith carbon dioxide in the previous experiments. Concrete mixes wereprepared as in the second experiment, except the dosages of carbondioxide used was 15 g per cylinder (1.9% carbon dioxide bwc). Inaddition, in one set of both control and carbon dioxide batches, thesecond water addition was increased to give a total water that was 4.7%increased over the default water addition 7-, 14-, and 28-daycompressive strength tests were conducted. The results are shown in FIG.9. Even with the additional water the concrete mix contacted with carbondioxide showed a 28-day strength comparable to control.

In a fourth experiment, various additional water amounts wereinvestigated. Concrete mixes were prepared as in the second experiment,except the dosages of carbon dioxide used was 10 or 15 g per cylinder(1.3 or 1.9% carbon dioxide bwc, respectively). In addition, in sets ofboth control and carbon dioxide batches, the second water addition wasincreased to give a total water that was 2100, 2200, 2300, 2400, or 2500ml/20 kg dry mix, compared to 2000 ml/kg for control batches. The amountof water on the first addition was 60% of the total water so the w/c attime of carbon dioxide was increased as mix water was increased. 7- and28-day compressive strength tests were conducted. The results are shownin FIGS. 10-13. Slump tests were also conducted and the results areshown in FIG. 14. Additional water partially compensated for thedecrease in slump with carbon dioxide addition, especially at the lowercarbon dioxide dose. 7 day strength was comparable to control for mostdoses of water.

Example 2

This example describes retrofitting an existing readymix truck with asystem for contacting a wet concrete mix in the drum of the truck withcarbon dioxide while the concrete mix is mixing.

A readymix concrete truck was retrofitted for delivery of carbon dioxideto the mixing concrete mix. A flexible rubber tube of approximately ¾″diameter was brought to the readymix site and the readymix truck wasretrofitted by running a flexible rubber tubing for delivery of carbondioxide in parallel with existing tubing for delivery of water to allowdelivery of carbon dioxide to the drum of the truck at the high end ofthe drum while a hydraulic cement mix, e.g., concrete, was mixing in thedrum. The opening of the tube was positioned 0.5 to 2 m from theconcrete in the truck. The truck was a six cubic meter transit mixer. Asource of carbon dioxide was attached to the flexible rubber tubing. Inthis example, the source of carbon dioxide was a liquid carbon dioxidesupply, heater (ethylene glycol), gas buffer tank, gas meteringequipment, and gas output, to supply carbon dioxide of at least 99%concentration. The gas delivery trailer took liquid carbon dioxide,metered by a pressure regulator and ran it through a heat exchangerwhere hot liquid glycol (antifreeze) heated it to change the liquidcarbon dioxide into a gas. The gas was stored in the receiver tanks on amobile cart which can be wheeled out of the trailer to a location insidethe plant. A touchscreen was used to program the correct dose of carbondioxide to be delivered during the concrete making process. Valves andsensors were used to meter the gas correctly. Hoses were used to connectbetween the trailer, cart and manifolds and the manifolds attach to theconcrete making machine to deliver the gas dose in the correct location.In industrial trials the gas line was ¾″ diameter.

In another readymix truck retrofit, the truck was retrofitted byconnecting the carbon dioxide source to the drum through the water linerelease. The water line went from the water tank on the truck to a Tjunction. Going up from the T sent the water into the drum. Going downfrom the T was a drain to empty the line onto the ground. The watersupply was turned off when not in use, essentially connecting the outletto the drum. By booking the gas supply into the outlet, in this example,the parallel line approach was avoided and it was only necessary to usea carbon dioxide supply and a conduit to connect to the T junction.

Example 3

This example describes the use of carbon dioxide to contact a mixingconcrete mix in a readymix truck.

The retrofitted readymix truck described in Example 2 was used. Thecomponents of a batch of concrete were added to the drum of the truck,including cement mix and aggregate. While the hydraulic cement mix wasmixing, carbon dioxide in a gaseous mixture that was at least 99% carbondioxide was introduced into the drum at a flow rate of 750, 1500, or2250 liters per minute for 180 seconds, for a total carbon dioxide doseof 0.5%, 1.0%, or 1.5% bwc, respectively. The drum remained open to theatmosphere during the carbon dioxide addition. After the flow of carbondioxide had stopped, additional water was added to the mixing concreteto bring the w/c ratio of the concrete to 0.45. The truck received theconcrete and the carbon dioxide at the batching bay, and delivered theconcrete to an adjacent building where testing was done and samples weremade. Tests were conducted for temperature, slump, and air content, andcylinders were made for strength and flexural strength.

In a second mixing example, carbon dioxide was added before anyadditional water was added to the mix, and the water in the mix duringcarbon dioxide addition was due to water in the aggregate mix, which hadbeen exposed to water before addition. The aggregate was wet and withthe addition of the wet aggregate the water content of the resultinghydraulic cement mix (concrete) was a w/c ratio of 0.17. Final mix waterwas achieved by adding water to the truck manually attain desiredconsistency.

Example 4

This example describes retrofitting a stationary pan mixer used to mixconcrete for use in a precast concrete operation with a system forcontacting the mixing concrete in the mixer with carbon dioxide. A gasline was attached to a carbon dioxide supply and run to a pan mixer formixing concrete for delivery to a mold. The line was configured to allowa controllable flow of carbon dioxide from the carbon dioxide to themixer for a predetermined time during mixing of the wet mix.

Example 5

This example describes the use of carbon dioxide to contact a mixingconcrete mix in a stationary pan mixer and pouring the concrete intomolds for precast concrete products. A retrofitted pan mixer asdescribed in Example 4 was used to deliver carbon dioxide to a wetconcrete mix in a mixer while the concrete was mixing, for 3 minutes, toobtain a dose of carbon dioxide of 0.5% to 2.5% bwc. The gas line wasabout 1 m from the concrete.

Example 6

This example describes the use of carbon dioxide to contact mixingconcrete mix in two different ready mix operations.

In a first operation, the following mix was used:

-   -   30 MPa with a maximum 4″ slump        -   20 mm aggregate—2780 kg        -   Sand—2412 kg        -   Washed sand—615 kg        -   Type 10 GU cement—906 kg        -   Fly ash—192 kg        -   Visco 2100—850 ml        -   ViscoFlow—1650 ml        -   Water—334 liters

The carbon dioxide was added via a ¾″ diameter rubber hose clipped tothe side of the truck and disposed in the mixing drum to deliver CO₂ tothe surface of the mixing concrete for 180 sec (controlled manually), atlow, medium or high dose, to achieve 0.43, 0.55, and 0.64% CO₂ bwc,respectively. Because the aggregate was wet, CO₂ was added to the mixbefore the final addition of water; the w/c of the mix when CO₂ wasadded was calculated to be 0.16. Final water was added immediately afterthe CO₂ addition.

The addition of CO₂ greatly reduced slump as time from arrival at siteprogressed, see FIG. 15. Carbonated concreted showed reduced strength at7 days compared to control, increasing in strength over time so that byday 56 the carbonated concrete was stronger than uncarbonated at alldoses tested. See FIG. 16. The addition of CO₂ caused an increase intemperature of the wet cement that was dose dependent, as shown in TABLE2.

TABLE 2 Effect of CO₂ dose on temperature, ready mix Mix Temperature (°C.) Control 15.2 0.43% CO₂ 17.0 0.55% CO₂ 18.4 0.64% CO₂ 19.4

Rapid chloride penetration tests (RCPT, using ASTM C1202 Standard TestMethod for Electrical Indication of Concrete's Ability to ResistChloride Ion Penetration) and flexural strength tests were alsoperformed. See FIG. 17. Although RCPT increased with carbonation (FIG.17A), since the control concrete was at the high end of low (generallyconsidered 1000 to 2000 coulombs) and the carbonated concrete was at thelow end of moderate (generally considered to be 2000 to 4000 coulombs)the difference was not considered to be significant. Flexural strengthdecreased slightly with carbonation (FIG. 17B).

In a second operation, mixes were prepared to meet a pre-determinedslump target of 5 inches, with additional water added to carbonatedbatches as necessary to achieve target slump.

The following mix was used:

-   -   Sand—770 kg/m³    -   20 mm Stone—1030 kg/m³    -   Cement GU—281 kg/m³    -   Fly Ash (F)—55 kg/m³    -   Water—165 L/m³    -   Daracem 50—1400 ml/m³    -   Darex II—200 ml/m³    -   Total—2301 kg    -   Water on CO₂ batches increased (unknown amount added after CO₂        injection ends) to achieve target slump.

CO₂ was introduced into the mixing drum of the ready mix truck via ahose connected at a T-junction to an existing water line that dischargedinto the mixing drum. As in the previous operation, because theaggregate was wet, CO₂ was added to the mix before the final addition ofwater; the w/c of the mix when CO₂ was added was calculated to be 0.16.Final water was added immediately after the CO₂ addition. Two doses ofCO₂ were used, 0.5% and 1.0% bwc, as well as an uncarbonated control.Additional water was added to the carbonated concrete to achieve targetslump. The concrete was used in a precast operation on site and arrived20-25 minutes after the mixing started.

The use of additional water brought the slump of the carbonated concreteto levels comparable to the uncarbonated control, as shown in TABLE 3:

TABLE 3 Slump, temperature, and air content of uncarbonated andcarbonated ready mix concretes Air Slump Temperature Mix Content (in) (°C.) Control 3.6% 5.5 23.9 0.5% 4.2% 4.5 26.2 CO₂ 1.0% 4.1% 5 28.6 CO₂

For the 0.5% carbonated concrete, two later slump measurements, at 20min and 35 min after arrival at the job site, were both 5 inches.Further measurements were not obtained for the 1.0% sample.

Compressive strengths of the batches are shown in FIG. 18. The 0.5% CO₂mix showed 85% strength compared to control at 1 day, equivalentstrength at 7 and 28 days, and 106% of control strength at 56 days. The1.0% CO₂ mix showed 71% strength compared to control, and 94% at 28 and56 days. The additional water added to achieve the target slump likelyreduced compressive strength of the concrete.

In a third operation, an admixture, sodium gluconate, was used torestore flowability.

The following mix was used:

-   -   Sand—770 kg/m³    -   20 mm Stone—1030 kg/m³    -   Cement GU—336 kg/m³    -   Water—163 L/m³    -   Daracem 55—1350 ml/m³

CO₂ was introduced into the mixing drum of the ready mix truck via ahose connected at a T-junction to an existing water line that dischargedinto the mixing drum. As in the previous operation, because theaggregate was wet, CO₂ was added to the mix without a first wateraddition, and before the final addition of water; the w/c of the mixwhen CO₂ was added was calculated to be 0.16. Final water was addedimmediately after the CO₂ addition. Two doses of CO₂ were used, 1.0% and1.5% bwc, as well as an uncarbonated control. Sodium gluconate was addedto the 1.5% CO₂ batch at dose of 0.05% bwc, after the addition of CO₂.The concrete was used in a precast operation on site and arrived 20-25minutes after the mixing started.

The use of the sodium gluconate brought the slump of the 1.0% carbonatedconcrete toward levels comparable to the uncarbonated control, as shownin TABLE 4:

TABLE 4 Slump, temperature, and air content of uncarbonated andcarbonated ready mix concretes Air Slump Temperature Mix Content (in) (°C.) Control 5.9% 7 25.8 1.0% 5.9% 4 28.1 CO₂ 1.5% 4.5% 3 28.6 CO₂

For the 1.0% carbonated concrete (with sodium gluconate), a later slumpmeasurements, at 20 min after arrival at the job site, was 5.5 inches.For the 1.5% carbonated concrete (no sodium gluconate), a later slumpmeasurements, at 15 min after arrival at the job site, was 3.0 inches.Carbon dioxide uptake of the 1.0% dose was 0.44% bwc, for an efficiencyof 44%. Carbon dioxide of the 1.5% dose was 1.69% bwc, or 113%efficiency.

Compressive strengths of the batches are shown in FIG. 19. The 1.0%concrete (with sodium gluconate) had a compressive strength of 96, 107,and 103% of control at 1, 28, and 56 days, respectively. The 1.5%concrete (no sodium gluconate) had a compressive strength of 98, 117,and 109% of control at 1, 28, and 56 days, respectively. The 1.5% CO2concrete had a reduces slump but was still usable.

This example illustrates that carbonation can reduce slump in wet mixused in ready mix operations. Depending on the mix, the slump may besuch that remedial measures, such as use of additional water, use ofadmixture, or both, are necessary; as illustrated by this example, thesemeasures can restore slump to acceptable levels without major alterationin the strength of the concrete.

Example 7

This example describes the use of an admixture to modulatecompactability/strength of a dry cast concrete mix. Several differenttests were performed.

Work had identified that carbonation of fresh concrete prior toformation reduced the mass of an industrially produced carbonated drymix product in certain mixes. Dry mix products are made to a constantdimension so lower mass resulted in lower density which can contributeto lower strength. A lab investigation pursued novel admixtures toaddress the density issue. Sodium gluconate was studied in a labprogram. In conventional concrete sugars are known to be set retarders.The work investigated its use in conjunction with carbonated freshconcrete to see if the sodium gluconate would act in relation to thereaction products causing the density issue.

In a first test, the mix design was a dry mix concrete with thefollowing proportions

-   -   1.75 kg cement    -   15.05 kg SSD (saturated surface dry) fine aggregate    -   7.00 kg SSD (saturated surface dry) coarse aggregate    -   1.19 kg mix water    -   Target water was 6.05% by mass of the concrete

The admixtures used were: 1) Sodium gluconate to improve density—it wasprepared as a solution of 36.8 g of sodium gluconate per 100 ml ofwater. It was dosed into the concrete as a mass of solid sodiumgluconate by weight of cement; 2) Rainbloc 80—a water repellencyadmixture for Concrete Masonry Units; and 3) ProCast 150—an admixturefor use in concrete masonry units. The two commercial admixtures weredosed based upon mL/100 kg cementitious materials as per manufacturer'sspecifications.

Samples were mixed according to the following procedure:

-   -   Aggregate is introduced first and mixed until homogenous.    -   Cement is introduced and mixed for 30 s until homogenous.    -   Mix water is added over 15 seconds.    -   The concrete is mixed for a total of 4 minutes starting from the        water addition.    -   In the case of CO₂ batches the following modified sequence was        used:    -   1 minute mixing all materials    -   Initial temperature is recorded    -   CO₂ gas is injected over the surface of the mixing concrete at        100 LPM for required time based on test plan. The gas is        nominally retained in the bowl by use of a cover that        accommodates the movement of the mixing mechanism. The mixing        proceeds during the gas delivery.    -   Final temperature is recorded.    -   Admixtures are introduced to mix—always post carbonation    -   Mix for additional time to attain a total of 4 minutes mixing.

Concrete samples were formed according to the following procedure

-   -   Concrete was formed into standard 100 mm diameter cylinder molds    -   3.5 kg of dry mix materials were introduced into the molds and        compacted using a specially designed pneumatic ram which applies        95-100 psi of pressure directly under vibration onto the cross        section of the concrete mass    -   A steel trowel was used to remove any excess materials from the        top of the mold and level the surface of the test specimen.    -   The mass of the cylinder was recorded.    -   Test specimens were set to cure in a lime water bath, in        accordance with ASTM C192

The first trial produced four concretes: 1) Control; 2) Control with0.05% sodium gluconate; 3) CO2; 4) CO2 with 0.05% sodium gluconate. Thecylinder unit mass (mass of a constant volume of concrete) wasunderstood as an estimate of product density. 6 samples were produced.

With the control density as the standard, the control with sodiumgluconate had a relative density of 98.8%, the carbonated concrete was94.0% and the carbonated concrete with sodium gluconate was 93.4%. Thus,addition of 0.05% sg to control reduces cylinder density 1.2%,application of CO₂ reduces cylinder density 6%, and addition of 0.05% sgto CO₂ treated concrete did not improve cylinder density. The dose istoo low.

In a second trial, the same conditions for sample preparation as for thefirst trial were used, with the following carbonation and sodiumgluconate conditions:

-   -   Uncarbonated with 0, 0.24% and 0.48% sodium gluconate    -   CO₂ for 1 minute with 0.06%, 0.12%, 0.24% and 0.48% sodium        gluconate    -   CO₂ for 2 minutes with 0.10%, 0.24%, 0.48% and 0.72% sodium        gluconate

The effects of various doses of sodium gluconate on density, which canbe considered a proxy for strength, is shown in FIG. 20. Applying CO₂decreased the cylinder unit mass (proxy for density). Increasing theamount of CO₂ absorbed by the concrete correspondingly increased theamounts of sodium gluconate to offset the density shortcoming.Increasing the sodium gluconate dose increased the density of allconcretes over the range considered. The control concrete cylinder unitmass increased 1.7% at a dose of 0.48% sodium gluconate. For 1 min ofCO₂ the sodium gluconate dosages of 0.24% and 0.48% both resulted in acylinder mass equivalent to the control. For 2 minutes of CO₂ thecylinder mass was 99% of the control at a sodium gluconate dosage of0.48% and and matched the control cylinder mass when the dose reached0.72%

In a third trial, the same conditions for sample preparation as for thefirst trial were used, with carbonation at 50 LPM for 90 seconds and thefollowing sodium gluconate conditions:

-   -   Control    -   CO₂ with 0.24% sodium gluconate    -   CO₂ with 0.30% sodium gluconate    -   CO₂ with 0.36% sodium gluconate    -   CO₂ with 0.42% sodium gluconate

Cylinder mass (density, assuming all cylinders are of equal volume) wasmeasured, and compressive strength measured at 1, 3, and 7 days.Cylinder densities are shown in FIG. 21. Applying CO₂ decreased thecylinder unit mass (proxy for density). Increasing the sodium gluconatedose increased the density over the range considered. The effectplateaued somewhat at the higher doses suggested the preferred dose ispotentially in the 0.30% to 0.42% range. Without gluconate the cylindermass of a carbonated product is about 7% less than the control. Agluconate dose of 0.30% brought the mass to 3% under the control. A doseof 0.42% brought the mass to 4% less than the control. The compressivestrengths of the sodium gluconate treated samples were comparable tothose of the control sample at doses of 0.30% and above.

In a fourth trial, the same conditions for sample prepration as for thefirst trial were used. Carbonation was at 50 LPM for 90 seconds and thefollowing sodium gluconate conditions:

-   -   Control    -   CO₂    -   CO2 with 0.30% sodium gluconate    -   CO2 with 0.42% sodium gluconate

All concretes contained Rainbloc (0.32%). It was added with the mixwater. The cylinder unit mass (mass of a constant volume) was measuredas a test of product density. 6 samples were produced. The strength wasmeasured at 1, 3 and 7 days. Cylinder densities are shown in FIG. 22.The application of CO₂ reduced the density (by 6%) and strength of theconcrete product The use of sodium gluconate improved the density andstrength. 0.3% sodium gluconate was sufficient to make carbonatedconcrete with 98.5% of the density of the control and equivalentstrength. 0.42% sodium gluconate produced carbonated concrete withequivalent density and strength to the control. The optimum dose forthis combination of cement and mix design proportions appears to be onthe order of 0.42% sodium gluconate by weight of cement.

In a fourth trial, the same conditions for sample prepration as for thefirst trial were used. Carbonation was at 50 LPM for 90 seconds and thefollowing sodium gluconate conditions:

-   -   Control    -   CO₂    -   CO₂ with 0.30% sodium gluconate    -   CO₂ with 0.42% sodium gluconate    -   CO₂ with 0.30% sodium gluconate with post-CO₂ addition of        Procast.

In contrast to the previous days the cement was a 70/30 blend of whitecement and OPC. All batches contained Rainbloc (0.32%) and Procast 150(0.64%). The Rainbloc was added with the mix water while the Procast 150was tried both as part of the mix water and as an addition after thecarbon dioxide treatment. The strength was measured at 1 (2 samples),and 7 days (4 samples). Cylinder densities are shown in FIG. 23. Thecarbonation treatment produced a compacted concrete product that was 7%less dense than the control. The density was improved by adding sodiumgluconate. A dose of 0.30% sodium gluconate improved the density to 97%of the control. A further increase to 0.42% produced a concrete productwith a density of 96%. As compared to the earlier trial that did notinclude Procast, it is clear that the optimum dosage is sensitive to thepresence of other admixtures. Adding the Procast after the carbondioxide treatment provided improved product density. The timing of theaddition of admixtures with respect to the carbon dioxide application isimportant.

This example illustrates that an admixture, sodium gluconate, can returndensity and compressive strength of carbonated dry mix samples to thoseof uncarbonated samples, that the effect is dose-dependent, and that thetiming of delivery of additional admixtures added to the mix can affectstrength development.

Example 8

This example illustrates the effects of various admixtures on theworkability of carbonated mortar mix, prepared as for a wet castoperation.

A mortar mix was prepared containing 535 g Portland cement (Holcim GU),1350 g sand, and 267.5 g water. CO₂ gas was introduced at 20 LPM whilemixing. The time of CO₂ delivery depended on the target CO₂ uptake, forexample, to achieve 1.1% bwc the delivery took 3 to 4.5 min.

Three admixtures were used: sodium gluconate, fructose, sodiumglucoheptonate. The admixtures were added to carbonated mortar atdosages of 0.05, 0.10 and 0.20% by weight of cement. The dosages reflectsolid mass of additive delivered in a solution. The mortars werecarbonated while mixing to an uptake of about 1.9% by weight of cement.The admixture was added after the carbonation: after carbonation thetemperature of the sample was measured, then the admixture was added andthe sample was remixed to homogenize.

The slump of the produced mortar was measured as an assessment ofworkability. Slump was measure immediately after the end of mixing usinga Cement & Mortar Testing Equipments Transparence Acrylic Mini SlumpCone Test Apparatus (NL SCIENTIFIC INSTRUMENTS SDN. BHD. Malaysia.).Samples were rodded in two lifts, TK.

Carbonation greatly decreased the mortar slump, while each of theadmixtures, added after carbonation, improved slump. The carbonatedslump matched the control upon addition of 0.05% fructose, 0.10% sodiumgluconate or 0.2% sodium glucoheptonate. See FIG. 24.

In a second test, mortar mixes were prepared and carbonated as above,and either fructose or sodium gluconate was added before (Pre), during(Mid), or after (Post) carbonation, and the CO₂ uptake as well as slumpwas measured in the mortar mix. It was seen that the addition ofadmixture either Pre or Mid carbonation did not appreciably correct thedecrease in slump caused by carbonation, whereas the addition ofadmixture Post carbonation greatly improved the slump (the apparentimprovement in slump in the sodium gluconate Pre sample can beattributed to the anomalously low carbon dioxide uptake of this sample);this was true for both sodium gluconate and fructose. See FIG. 25.

Example 9

This example illustrates the effect of the time of addition of admix onworkability and strength development in a carbonated mortar mix, as fora wet cast operation.

In a first test, mortar mix was prepared containing 535 g Portlandcement (Holcim GU), 1350 g sand, and 267.5 g water. CO₂ gas wasintroduced at 20 LPM while mixing. The time of CO₂ delivery depended onthe target CO₂ uptake, for example, to achieve 1.1% bwc the deliverytook 3 to 4.5 min. Mortar cubes were created with C109M-12 Standard TestMethod for Compressive Strength of Hydraulic Cement Mortars. All samplescontained 0.10% bwc PCE (Mighty 21ES by Kao Chemicals) to assist castingof cubes.

Sodium gluconate was added either before or after carbonation, at 0,0.025, 0.05, and 0.075% bwc. Compressive strength at 24 hours wasmeasured at 24 hours and compared to uncarbonated control. See FIG. 26.The sodium gluconate added after carbonation did not affect the 24-hourcompressive strength, whereas sodium gluconate added before carbonationimproved 24-hour compressive strength, but the mix was found to bestiff. The mix with sodium gluconate added after carbonation wasworkable, but strength development was adversely impacted.

In a second test, mortar was prepared and carbonated with or withoutsodium gluconate, added before or after carbonation, as in the firsttest, except the cement was Lehigh cement. The results were similar tothose for mortar prepared with Holcim cement: When added after CO₂ theadmix was a retarder and resulted in lower strengths at 24 hours. Whenadded before the CO₂ the retarding effect was not evident and 24 hstrength was ˜90% of control with relatively small SG dosages.

Example 10

This Example illustrates the effects of system temperature on carbondioxide uptake in a wet mix.

In a first test, an experiment was conducted to look at the effect ofthe initial temperature of the materials on the carbonation behaviour offresh cement paste. Three target starting temperatures were considered,7° C., 15° C. and 25° C. (actual temperatures were ±2° C.). Measurementsinclude the mortar temperature, mini-slump (vertical slump and lateralspread), carbon dioxide uptake, and cube strength.

A mortar mix was prepared containing 535 g Portland cement (Holcim GU),1350 g sand, and 267.5 g water. The mix was brought to 7, 15, or 25° C.,and CO₂ gas was introduced at 20 LPM while mixing. The time of CO₂delivery depended on the target CO₂ uptake, for example, to achieve 1.1%bwc the delivery took 3 to 4.5 min. CO₂ uptake at various time pointswas measured. Slump measurements were also taken at various time points.

The effect of temperature on rate of carbon dioxide uptake is shown inFIG. 27, where the upper line and points are for 25° C., the middle lineand points are for 15° C., and the lower line and points are for 7° C.Rate of uptake of carbon dioxide increased as temperature increased; therate was 0.087% bwc/min at 7° C., 0.231 bwc/min at 15° C., and 0.331bwc/min at 25° C. The rate of carbon dioxide uptake increased 278% astemperature increased from 7 to 25° C.

The effect of temperature on slump is shown in FIG. 43. There was littleeffect on the workability with uptake of the mortar prepared at 7° C.(upper line and points). The workability of the mortar prepared at 15°C. declined rapidly with increasing uptake (lower line and points). Theworkability of the mortar prepared at 25° C. was between that of the twoother mortars declining with uptake but taking higher uptakes than the15° C. sample to reach zero workability (middle line and points).

In a second experiment, the effect of carbon dioxide temperature (heatedor unheated (cold) or form (dry ice), in some cases combined with theuse of ice water, on carbon dioxide uptake was measured in a cementpaste system. Cement, mix water (untreated or ice water) and admix weremixed for 30 seconds in blender, and initial properties and temperatureof the paste were evaluated. The paste was then carbonated while mixingin the blender. Carbonate while mixing in the blender, using heated gas,unheated gas (cold gas), or dry ice. Evaluate the final properties andtemperature of the paste. FIG. 28 shows the results of the study. Heatedor cold gases seemed to give approximately equivalent uptake. The mixeswith cold temperature (cold mix water, dry ice) did not give improvedcarbon dioxide uptake.

Example 11

This example illustrates the beneficial effect of calcium containingcompounds added before carbonation on 24 hour strength development in acarbonated mortar mix.

A mortar mix was prepared containing 535 g Portland cement (Holcim GU),1350 g sand, and 267.5 g water. CO₂ gas was introduced at 20 LPM whilemixing. The time of CO2 delivery depended on the target CO₂ uptake, forexample, to achieve 1.1% bwc the delivery took 3 to 4.5 min. Mortarcubes were created with C109M-12 Standard Test Method for CompressiveStrength of Hydraulic Cement Mortars. A plasticizer (0.10% Mighty21ES+0.10% Sika VF) with or without Ca(OH)₂ (2.0% bwc) was added beforecarbonation, and effects on 24-hour compressive strength were measured.The results are shown in FIG. 29. Carbonation decreased the 24 hourstrength of the mortar. The use of a plasticizer improved the strengthof both carbonated and control mortars. The further addition of Ca(OH)₂decreased the 24 hour strength of the control product but furtherincreased the 24-hour strength of the carbonated product.

In a second experiment, CaO (1.5%), NaOH (2.2%), Ca(NO₂)₂, or CaCl₂(3.0%) were added before carbonation to a mortar mix as above. Resultsare shown in FIG. 30. All calcium compounds showed benefits for strengthdevelopment in the carbonated mortar mix, relative to carbonated mortarmix with no admixture added.

Example 12

This example illustrates that the timing of addition of an admixtureused for conventional purposes, in this case an air entrainer, relativeto carbonation, may be important to retain the effect of the admixture.

A calcium hydroxide slurry was used as a test system. 20 g of Ca(OH)₂was mixed with 40 g water to form a slurry. CO₂ gas was injected intothe slurry at 5 LPM. The temperature, an indicator of carbon dioxideuptake, was measured over a 9-minute period. The plain slurry containedno admixture, while the slurry with an air entrainer contained 2.5% (bymass of Ca(OH)₂ of a liquid solution of hydrocarbons used for airentrainment in concrete (AirEx-L, Euclid Chemical). The carbon contentwas quantified using a combustion infrared detection carbon analyzer(Eltra CS 800, Eltra GmbH, Germany). The net % CO₂ increase wascalculated in comparison to a base uncarbonated system containing thecomponents.

After 10 minutes of carbonation, the slurry without an additive showed aCO₂ uptake that was 25.5% of the original solid mass, while the slurewith the air entrainer additive had an uptake that was 36.2%; thus, thesurfactant admixture increased the CO₂ uptake by 42.1%.

In a second test, various surfactants were tested for their effects onCO₂ uptake. Standard mortar mix, as in Example 8, was used, and thesurfactants were dosed at 0.10% bwc. CO₂ as injected for 6 minutesduring mixing. Initial and final temperatures were measured and netincrease in CO₂ content was measured as above. The results are shown inTABLE 5.

TABLE 5 Effects of surfactants on CO2 uptake Initial Final Temp, Temp,Temp Net CO₂ Additive Source ° C. ° C. Change CO₂ % increase None 23.833 9.2 1.65 Baseline Sunlight Dish soap 24.1 41.4 17.3 2.89 75% SunlightDish soap 24.1 41.9 17.8 3.34 102%  MB AE-90 BASF 23.4 33 9.6 1.80  9%Solar: w Guelph 23.8 35.2 11.4 2.17 31% Soap AirEX-L Euclid 23.8 40.616.8 2.84 72%

In a third test, mortar batches as above, containing 0.1% bwc of asurfactant air entrainer (Euclid AirEx-L), or no surfactant (control)were exposed to CO₂ during mixing for 0, 2, 4, or 6 minutes, and the CO₂uptake measured. There was greater uptake in the mortar treated with airentrainer than in control, untreated mortar at all time points, but therelative improvement was greater at the low exposure times: there was a117% increase in CO₂ uptake compared to control at 2 min, a 104%increase in CO₂ uptake at 4 minutes, and a 28% increase in CO₂ uptake at6 min.

In a fourth test, the effect of CO₂ addition before or after addition ofan air entrainer on mortar density was tested. A lower unit weightindicated a higher air content. Four air entrainers were used: EuclidAir-Ex-L, Grace Darex ii, BASF MB-AE 90, and Grace Darex AEA ED. Theresults are shown in FIG. 31. In all cases, addition of the airentrainer pre-CO₂ treatment led to an increase in density, whereasaddition of the air entrainer post-CO₂ treatment resulted in a densitythe same as untreated mortar.

This Example illustrates that the timing of CO₂ treatment relative toaddition an air entrainer affects rate of CO₂ uptake and density. If itis desired to maintain the density effect of the air entrainer, itshould be added after CO₂ addition. In some cases, a two-dose approachcould be used where an early dose of air entrainer is used to enhanceCO₂ uptake, then a later dose to achieve desired effects on density.

Example 13

This Example describes tests of carbonation in a precast dry mixoperation. Tests were conducted at a precast facility in which aconcrete mix was carbonated at different stages of the casting process,in some cases using a sodium gluconate admixture at variousconcentrations. The effects of carbonation, with and without admixture,on strength and water absorption were measured.

The concrete mix shown in TABLE 6 was used.

TABLE 6 Standard Block Design Component Name Amount Coarse aggregateBirdseye Gravel  685 lb Fine aggregate Meyers Mat Torp Sand 4320 lb Fineaggregate Silica Sand/Wedron 430 1250 lb Cement Illinois Product 1000 lbAdmixture Rainbloc 80  50 oz Target water content 6.5%

The aggregates, cement and water were added to a planetary mixer. Carbondioxide was flowed into the mixer via a ¾ inch diameter rubber pipe for180 s at a flow rate to achieve the desired carbonation. In some runs,carbon dioxide was added both at the mixer and at the feedbox. In apreliminary run, all water was added initially, but in subsequent runs,additional water was added about halfway through the 180 s according toan assessment of the mix consistency prior to the completion of the mixand additional water was added as necessary to achieve a desired mixlook. Batches with carbon dioxide delivered to the concrete requiredadditional water nearly in proportion to the amount of carbon dioxidegas supplied. The concrete mix was placed in a mold to produce 8 inchblocks, which were tested for density, compressive strength at 7, 28,and 56 days, and water absorption (all according to ASTM C140, 5 blocksper test). The carbonation of the concrete was also determined: Thesamples for analyzing the carbon dioxide content of the concrete werecreated by taking a fresh sample from the production line, drying theconcrete on a hot plate to remove the water, and subsequently sievingthe material through a 160 μm sieve. Samples of the raw materials wereexamined to determine how much of each component passes a 160 μm sieveand the carbon content of the passing material. This information, alongwith the concrete mix design, allows for the calculation of atheoretical control carbon content against which analyzed samples can becompared. The carbon content was quantified using a combustion infrareddetection carbon analyzer. The net % CO₂ increase was calculated incomparison to a base uncarbonated system containing the components.

In a first test, carbonation at both the feedbox and mixer or just thefeedbox was tested. The variations examined are summarized in TABLE 7,below. Data for controls, which were prepared on other days (samples 500and 700), are also presented.

TABLE 7 Standard Block Production Variables and Water Contents TotalDose Water Code Condition Mode (% bwc) w/c fraction 0600 ControlUncarbonated — 0.392 6.64% 0601 CO₂ Feedbox 0.5% 0.5% 0.422 8.32% 0602CO₂ Mixer 0.5% 0.5% 0.430 8.25% 0603 CO₂ Mixer 1.0% 1.0% 0.440 8.08%0604 CO₂ Mixer 1.0%, Feedbox 1.5% 0.450 8.23% 0.5% 0605 CO₂ Mixer 1.5%1.5% 0.455 8.39% 0500 Control Uncarbonated — 0.406 8.88% 0700 ControlUncarbonated — 0.426 7.45%

FIG. 32 shows the results of tests for carbon dioxide uptake,compressive strength, water absorption, and density for the blocksproduced in this test.

The efficiency of carbon dioxide uptake was greatest in the 1.5% bwcdose where carbon dioxide was delivered only to the mixer (batch 0605);delivery of 0.5% of the dose at the feedbox was consistently lessefficient than delivery of all of the same dose at the mixer (batch 0601compared to batch 0602; batch 0604 compared to batch 0605). A carbondioxide uptake efficiency of 93% was achieved with a CO₂ dose of 1.5%delivered solely at the mixer (batch 0605). Consequently, in subsequenttests a dose of 1.5% CO₂, delivered solely at the mixer, was used.

The addition of CO₂ to the mix consistently improved compressivestrength at 7, 28, and 56 days, at all doses tested, whether or not theCO₂ was added at the mixer, the feedbox, or both. The overall averagecompressive strengths of the two (uncarbonated) control sets (0500 and0700) were 2843, 3199, and 3671 psi at 7, 28, and 56 days, respectively.At 7 days the first four batches made with CO₂ (0601, 0602, 0603, and0604) showed a 30-36% strength benefit over the average control, and thefinal carbonated batch (0605) was 18% stronger. The strength benefit wasmaintained at 28 days with a benefit of the first four carbonatedconditions ranging from 29037% and the final batch being 19% better thanthe average control. The 56 day results indicated the strength benefithad increased to 30-45% for the first four sets and 36% for the finalset.

Water absorption was reduced through carbonation. Mixes 0601 to 0603 hada water absorption about 35% lower than that of uncarbonated control(0500 and 0700), and mixes 0604 and 0605, in which 1.5% CO₂ was added,had a water absorption of about 18% lower than control.

Density of the carbonated mixes varied with amount of carbon dioxideadded. The density of the two lowest CO₂ (0.5%) batches (0601 and 0602)was about 2.5% higher than control, but the density of the batchescarbonated at a dose of 1.0 or 1.5% (0603, 0604, and 0605) wereequivalent to the density of the control.

Overall, this test indicated that carbonation of this mixture in aprecast operation producing 8 inch blocks indicated that an efficiencyof carbon dioxide uptake of over 90% could be achieved, producing blocksthat were stronger than uncarbonated at all carbon dioxide doses andtime points tested, culminating in a 56 day strength that averaged over30% greater than control. Water absorption of the carbonated blocks wasconsistently lower than control, and the blocks carbonated at 1.0 and1.5% CO₂ dose had a density the equivalent of uncarbonated blocks.

In a second test, the mix of TABLE 8 was used, with a dose of 1.5% CO₂,delivered at the mixer, and, in addition five different doses of asodium gluconate admixture were delivered—0.1, 0.2, 0.3, 0.4, and 0.5%bwc. The sodium gluconate was delivered in water solution, dissolved onegallon of water (0.1, 0.2, and 0.3%) or in two gallons of water (0.4 and0.5%). The sodium gluconate admixture was added about 75 s after carbondioxide delivery to the mixer started, and took about 90 s to add.Admixture was added manually during the mixing cycle. The addition ofadmixture was begun during the carbon dioxide addition so as not toextend the mixing cycle. Carbonation, compressive strength, density, andwater absorption were measured.

The investigated variables and water contents are summarized in TABLE 8.The overall results are summarized in FIG. 32.

TABLE 8 Standard Block, with sodium gluconate CO₂ Dose Sodium CodeCondition Mode (% bwc) gluconate w/c Water fraction 0700 Control — — —0.425 7.35% 0701 CO₂ Mixer 1.5 0.5% 0.413 8.12% 0702 CO₂ Mixer 1.5 0.4%0.413 7.85% 0703 CO₂ Mixer 1.5 0.3% 0.424 7.99% 0704 CO₂ Mixer 1.5 0.2%0.426 7.87% 0705 CO₂ Mixer 1.5 0.1% 0.433 7.81% 0706 Control — — — 0.4267.45%

The efficiency of CO₂ delivery for batches produced in this test wasfound to range from 78% to 94%, across all batches. The gas injectionparameters were held constant and the average efficiency was found to beabout 85%.

It was shown that the strength was sensitive to the admix dose. See FIG.33. The control strength can be taken at 100% at all ages and thecarbonated strengths are shown in relative comparison. For the lowerdoses the carbonated concrete strength was equivalent to the controlstrength at both 7 and 28 days. For a dose of 0.4% there was a 12%strength benefit at 7 days and equivalent performance at 28 and 56 days.For a dose of 0.5% there was a 34% strength benefit at 7 days, 28% at 28days, and 25% at 56 days. These results indicate that there is a certainamount of admixture required in the concrete beyond which a strengthbenefit can be realized.

It is shown that the water absorption was again reduced for thecarbonated products. All carbonated mixes were dosed with 1.5% CO₂ bwcand had similar uptakes. The water absorption was reduced 12% for thelowest and 31% for the highest admixture dose. The density showed somedependence on admixture dosage. The carbonation treatment with the smalldose of admixture decreased the density from 131 to 128.5 lb/ft³ (thoughit can be noted that the strength remained equivalent to the control).The density increased with admixture dose and equivalent density wasfound with a dose of 0.3% and density was 1.3% higher for the highestadmix dose.

This Example illustrates that carbon dioxide can be added to a precastconcrete mix in a dry cast operation at the mixer stage and the productsformed are generally stronger, show lower water absorption, andequivalent density when compared to non-carbonated products. Theaddition of a sodium gluconate admixture resulted in a dose-dependenteffect on strength, water absorption and density, and indicated that anoptimum dose for admixture can be achieved to optimize these parameters.

Example 14

In this example the same precast equipment was used in the same facilityas in Example 13, but using three different concrete mixes: a limestonemix, a lightweight mix, and a sandstone mix. This example illustratesthe importance of adjusting carbonation mix parameters to mixes withdifferent characteristics.

Three different mix designs were used, shown in TABLES 9, 10, and 11.

TABLE 9 Limestone Block Mix Design Component Name Amount Coarseaggregate Sycamore FA-5 3152 lb Coarse aggregate Sycamore FM-20 5145 lbFine aggregate Silica Sand/Wedron 430 745 lb Cement Illinois Product 351lb Cement White Cement 819 lb Admixture Rainbloc 80 59 oz AdmixtureFrocast 150 117 oz Target water content 8.6%

TABLE 10 Lightweight Block Mix Design Component Name Amount Coarseaggregate Birdseye Gravel 1030 lb Coarse aggregate Gravelite 1500 lbFine aggregate Screening Sand 2200 lb Fine aggregate Meyers Mat TorpSand 1500 lb Cement Illinois Product 725 lb Admixture Rainbloc 80 34 ozTarget water content 7.9%

TABLE 11 Sandstone Block Mix Design Component Name Amount Coarseaggregate Sycamore FA-20 3750 lb Fine aggregate Meyers Mat Torp Sand1800 lb Cement Illinois Product 730 lb Admixture Rainbloc 80 37 ozTarget water content 7.0%

Limestone Mix Test.

In a first test, the limestone mix of TABLE 9 was used. Conditions wereas for the second test of Example 13, with CO₂ added at a dose of 1.5%in the mixer. Addition of 0.4% sodium gluconate was tested. The additionof the Procast admixture that is normally part of the mixing sequencefor the limestone mix design was delayed to be added after the carbondioxide injection was complete. The investigated variables and watercontents are summarized in TABLE 12. The overall results are summarizedin FIG. 34.

TABLE 12 Limestone Mix Production Variables and Water Contents CO₂ MixDose Water Code Design Condition Mode (% bwc) Admix w/c fraction 0805Limestone Control — — — 0.225 7.75% 0806 Limestone CO₂ Mixer 1.5 0.4%0.514 8.53%

The limestone mix design was examined in only a limited production runpartly due to the perceived difficulty of accurately assessing the netamount of absorbed carbon dioxide against the high carbon content of thelimestone background, at least when using the current analytical methodsand procedures.

The compressive strength data showed that the carbonated limestoneblocks averaged 2349 psi at 7 days and were slightly weaker (7%) thanthe control blocks. The 28 day strength was 2518 psi and 14% lower thanthe control. The 56 day strength averaged 2762 psi and 9% weaker thanthe control though this gap could be narrowed to 6% if an outlier pointwas removed. The dose of admixture in this test was determined using theIllinois Product cement and no advance tests on the Federal White cementused in the limestone mix design were performed. Subsequent labdevelopment has made it clear that the effect and dosage of theadmixture is sensitive to cement type. The integration of thecarbonation technology may require a small investigative series of trialruns to determine both if the admixture is desired and what the properdose should be. The success at demonstrating the admixture usage, forthe Illinois Product cement, in the lab prior to the pilot suggests thatpreliminary optimization screening could be accomplished for any mix forwhich the materials were available.

In terms of water absorption, it was found that the carbonated limestoneblock had a higher absorption and lower density than the control blocks.The absorption was increased 18% and the density was decreased 2%. Theresults agree with the lower strength of the carbonated limestone blocksand support the need to fine tune the inputs used when carbonating thismix.

Lightweight Mix Test.

In a second test, the lightweight mix of TABLE 10 was used. Conditionswere as for the second test of Example 13, with CO₂ added at a dose of1.5% in the mixer. Addition of sodium gluconate at three differentlevels, 0.35, 0.4, and 0.45% was tested. The investigated variables andwater contents are summarized in TABLE 13. The overall results aresummarized in FIG. 35.

TABLE 13 Lightweight Mix Design Production Variables and Water ContentsCO₂ Dose (% Code Mix Design Condition Mode bwc) Admix w/c Water fraction0801 Lightweight Control — — — 0.745  6.96% 0901 Lightweight CO₂ Mixer1.5 — 0.691 12.25% 0902 Lightweight CO₂ Mixer 1.5 0.35% 0.703 13.79%0802 Lightweight CO₂ Mixer 1.5 0.40% 0.758  8.80% 0903 Lightweight CO₂Mixer 1.5 0.45% 0.707 13.99%

Preliminary results suggest that an increase in CO₂ content similar towhat has been observed for the Standard Block occurred for carbonatedLightweight mixes in all cases. However, due to inherent difficultiesperforming carbon quantification for these mix designs a definitiveanalysis was not performed, and actual numbers obtained, in some casesover 100%, are not reliable.

The compressive strength data for the lightweight mix is summarized inFIG. 36. The testing broke three blocks from the control set and fiveblocks from each of the carbonated sets. The control (uncarbonated, nosodium gluconate) strength can be taken at 100% at all ages and thecarbonated (with and without sodium gluconate) strengths are shown inrelative comparison. The carbonated batch with no sodium gluconate wasslightly behind the control at 7 days but developed strength at a fasterrate thereafter. The admixture batches were found to be stronger at thefirst measurement and maintained at least this level or benefit throughthe remainder of the test program.

The lightweight block production found an optimal or near-optimal amountof admixture. With no admixture used the strength was 11% behind thecontrol strength at 7 days, 5% ahead at 28 days and 10% ahead at 56days. The carbonated concrete with low admixture dose was 22%, 42% and41% stronger than the uncarbonated control at 7, 28 and 56 daysrespectively. The 0.40% dose produced concrete that was 76%, 94% and 84%stronger at the three ages while the 0.45% dose of admixture resulted in21%, 32% and 33% improvements. These results are different than thosefor Standard Block in Example 13, where an optimal dose of sodiumgluconate was not necessarily reached even at 0.5%, and illustrates theusefulness of pre-testing, or otherwise optimizing, admixture dose andother conditions specific to a specific mix design. See Example 15 for afurther testing of this.

CO₂ injection had little effect on the lightweight block density orwater absorption when no sodium gluconate was used. Across the dosagesof admixture the water absorptions were decreased about 10% for the0.35% and 0.45% doses and 34% for the middle dose of 0.4%, compared touncarbonated control without sodium gluconate. Conversely, the densityincreased when sodium gluconate was used. It was up 1-2% for high andlow doses and 7% higher for the middle dose, compared to uncarbonatedcontrol without sodium gluconate. While the middle dose carbonatedblocks were the strongest and had the lowest water absorption they werealso the highest density. Promising strength and absorption results werefound with the other two admixture dosages and accompanied by a smalldensity increase. Admixture usage will generally benefit frompre-testing or other predictive work to optimize conditions to obtainthe desired result, e.g., in the case of lightweight blocks, acombination of strength, density, water absorption, and other propertiesas desired.

Sandstone Mix Test.

In a third test, the sandstone mix of TABLE 11 was used. Conditions wereas for the second test of Example 13, with CO₂ added at a dose of 1.5%in the mixture Addition of 0.35, 0.4, and 0.45% sodium gluconate wastested. The investigated variables and water contents are summarized inTABLE 14. The overall results are summarized in FIG. 37.

TABLE 14 Sandstone Mix Design Production Variables and Water ContentsMix Con- CO₂ Dose Ad- Water Code Design dition Mode (% bwc) mix w/cfraction 0803 Sandstone Control — — — 0.672 6.55% 0904 Sandstone CO₂Mixer 1.5 — 0.697 6.93% 0905 Sandstone CO₂ Mixer 1.5 0.35% 0.736 7.00%0804 Sandstone CO₂ Mixer 1.5 0.40% 0.710 7.29% 0906 Sandstone CO₂ Mixer1.5 0.45% 0.718 7.02%

Preliminary analysis of the Sandstone samples found CO₂ contents to behigher in all carbonated mixes relative to the control. The averageefficiency of CO₂ delivery for batches produced was found to range from20% to 90% at a 1.5% by weight of cement CO₂ dose. From the preliminaryanalysis batch 0905 appears to contain a smaller amount of captured CO₂compared to other batches produced under similar conditions. Furtheranalysis is currently underway to confirm this result. The averageefficiency of CO₂ delivery considering all Sandstone batches isapproximately 66%, however rises to approximately 81% if batch 0905 isomitted from the calculation.

The compressive strength data for the sandstone mix is summarized inFIG. 38. The testing broke three control blocks and five carbonatedblocks. The data is plotted to show every individual break with theaverage compressive strength highlighted. The sandstone carbonatedblocks with no admixture had a strength that was functionally equivalentto the control (carbonated, no admixture) strength (4% behind at 7 days,2% ahead at 28 days and 5% behind at 56 days). Of three doses ofadmixture, strength increased with admixture dosage suggesting that thedosage was reaching an optimum across the range considered. The 7 daystrength benefit was 7%, 9% and 63% on the three admixture dosagesconsidered. The benefit at 28 days was 8%, 22% and 63% respectively. At56 days was 9%, 8% and 58% respectively The strength increase withadmixture dose across the range of dosages mirrors the data with theStandard Block of Example 13 wherein some “threshold” amount of admixseems to be crossed in relation to the amount of carbon dioxide presentin the concrete.

The carbonation treatment without using the admixture increased thewater absorption 12% and decreased the density 3%. The use of admixturebrought the metrics back in line with the control at the lowest dose andoffered significant improvement at the highest dose. The waterabsorption was reduced 19% and the density was increased 3% for thecarbonated blocks with 0.45% dose of the admixture. As with other mixes,the final desired properties of the blocks will determine whetheradmixture, such as sodium gluconate, is used, and under what conditions,e.g., at what concentration, which can be pre-determined by preliminarytesting or by other means.

This Example illustrates the importance of tailoring carbonationconditions, e.g., admixture usage, to the exact mix design beingconsidered, in that the three mixes used showed differing responses tosodium gluconate as an admixture, and also had different requirements.For example, in the lightweight mix, density is an importantconsideration and may dictate that a lower dose of admixture be usedthan that that produces maximum strength development and/or minimumwater absorption. For other mixes, other considerations may play adominant role in determining carbonation conditions, such as use ofadmixture.

Example 15

This Example illustrates the use of a sodium gluconate admixture with amedium weight mix design, where the admixture dose was pre-determinedbased on results from the batches tested in Examples 13 and 14.

A Medium Weight mix design was used at the same facility and with thesame equipment as in Examples 13 and 14. The mix design is given inTABLE 15.

TABLE 15 Medium Weight Mix Design (target w/c = 0.78) Ingredient AmountFraction Birdseye Gravel 1030 lbs 12.8% Illinois Product Cement  675 lbs8.4% McCook Block Sand 1800 lbs 22.3% Meyers Torp Sand 2270 lbs 28.1%Screening 2300 lbs 28.5% RainBloc 80  34 oz —

It was found that the best dose of sodium gluconate in the Standard,Lightweight, and Sandstone mixes used in Examples 13 and 14 was linearlyrelated to cement content. See FIG. 39. Based on this relationship, andadjusted for the fact that the CO₂ dose was to be 1.0% rather than 1.5%used in the Standard, Lightweight, and Sandstone, a sodium gluconatedose of 0.25% bwc was used. Blocks were produced as described in Example13, with uncarbonated−sodium gluconate (control), uncarbonated+sodiumgluconate, carbonated−sodium gluconate, and carbonated+sodium gluconate,and tested for compressive strength and density. The blocks were alsosubmitted for third party testing which also included water absorption(Nelson Testing Laboratories, Schaumberg, Ill.).

Compressive strength and mass results for 7, 28, and 56 days aresummarized in FIG. 40. The direction of the arrows represents time ofmeasurement, from 7 to 56 days. The uncarbonated blocks with sodiumgluconate were slightly denser and stronger than uncarbonated blockswithout sodium gluconate at all time points tested, while the carbonatedblocks without sodium gluconate were lower in strength and mass thanuncarbonated without sodium gluconate, and the carbonated with sodiumgluconate were both stronger and lighter than the uncarbonated withoutsodium gluconate.

The results of third party testing are shown in FIG. 41. Three blockdata sets were used, with all batches meeting ASTM C90 specification.CO₂ alone made the blocks 6% weaker than control, but using CO₂ plussodium gluconate made it 8% stronger than control. CO₂ alone increasedwater absorption by 7% compared to control, but CO₂ plus sodiumgluconate resulted in blocks with 4% lower water absorption compared tocontrol. Shrinkage was increased for both CO₂ and CO₂ plus gluconatesets, but for the sodium gluconate batch it was effectively equivalentto the control.

This Example demonstrates that a pre-determined sodium gluconate dosefor a new mix, based on previous results, was sufficient to producecarbonated blocks comparable in mass and shrinkage, greater incompressive strength, and lower in water absorption than uncarbonatedblocks without sodium gluconate.

Example 16

The following protocols were used in EXAMPLES 17 TO 21, withmodifications as indicated in particular examples.

Mortar Mix

-   -   1. Prepare the mixing bowl by dampening the sides with a wet        cloth, be sure to remove any pooling water from the bowl before        introducing raw materials.    -   2. Weigh the necessary amount of water for your test and add the        water to the damp, empty mixing bowl.    -   3. Add sand to mixer    -   4. Blend sand and water for 30 seconds on Speed #2    -   5. Scrape the sides of the bowl with pre wet rubber spatula to        remove any materials sticking to the sides of the mixing bowl    -   6. Add the required cementitious materials to the mixing bowl    -   7. Blend Sand, water and cementitious materials for 30 seconds        at Speed #2    -   8. Record the time that cementitious materials are added to the        mix    -   9. Scrape the sides of the mixing bowl with a pre wet rubber        spatula    -   10. Record the temperature    -   11. If you are not carbonating, skip to step 14    -   12. Carbonate at a flow rate of 20 liters per min for desired        duration.    -   13. Record final temperature    -   14. Scrape the sides of the bowl with pre wet rubber spatula    -   15. Introduce necessary admixtures—the mixing sequence and        dosing details of the admixtures and additives may vary        according to test. Record time and dosage.    -   16. After each admixture or sugar is added, blend for 30 seconds    -   17. Measure slump using the Japanese slump cone. Record slump        and spread (two measurements).    -   18. For slump retention, return to bowl, wait, remix 30 sec        before next slump.    -   19. Produce a sample for calorimetry    -   20. Fill three mortar cubes molds with mortar (Procedure ASTM        C109/C109M-12 Standard Test Method for Compressive Strength of        Hydraulic Cement Mortars)    -   21. Cover mortar cubes with a plastic garbage bag or damp cloth        and demold only after 18+/−8 hours have passed    -   22. Break cubes at 24 hours+/−30 minutes (use time that cement        was introduced into the mix as an indicator of when samples        should be broken)

Concrete Mix

-   -   Wet inside mixer, add all stone and sand, mix 30 seconds to        homogenize    -   Add all cementitious materials, mix one minute to homogenize    -   Add all batch water over a period of 30 seconds, mix all        materials for one minute    -   Take initial temperature    -   Control batch—mix for 4 minutes and take final temperature. Add        admixtures as required, mix one minute    -   Carbonated mix—inject CO₂ gas at 80 LPM, enclose mixer, mix        while carbonating for required time    -   Remove cover and record final temperature, Add admixtures as        required, mix one minute    -   Record slump (ASTM C143) and cast 6 compressive strength        cylinders (ASTM C192)    -   Take two samples for moisture/carbon quantification bake off,        one sample for calorimetry    -   Demold cylinders after 28+/−8 hours and place them in a lime        water bath curing tank at a temperature of 23° C.+/−3° C.    -   Test compressive strength 24 hours (3 samples) and 2 at 7 days        (2 samples)

Example 17

In this Example the carbon dioxide uptake of cements from two differentsources, Lehigh and Holcim, were compared.

Mortar mix made under a 20 LPM flow of CO₂ gas. Samples were removedfrom the batch of mortar every 60 s until the 8 minute point. The carbondioxide content was measured and a curve constructed relating the lengthof exposure to CO₂ gas to the approximate amount of CO₂ uptake. Twocements were compared. Mix design was 1350 g EN sand, 535 g of cement,267.5 g of water. w/c=0.5.

The results are shown in FIG. 42. Carbon dioxide uptake increased withtime, as expected, but the rate of increase was different for the twodifferent cements. At a w/c of 0.5, the mortar paste can absorb carbondioxide but to exceed 1% uptake would take 3 to 5 minutes, depending onthe cement type used.

This Example illustrates that a w/c of 0.5 allows carbon dioxide uptake,but at a rate that may not be compatible with mix times in somesettings, and that the source of the cement can affect the properties ofa hydraulic cement mix made with the cement regarding carbon dioxideuptake.

Example 18

In this Example, the effect of w/c ratio on carbon dioxide uptake wasstudied.

In a first study, a test performed with mortar. The total mix was 990 gof Ottawa sand, 440 g cement, with 206 g of total water. Water, sand andcement were mixed, with the water added in two stages. CO₂ was suppliedfor various times at 10 LPM after the first water addition, whichbrought the mix to either 0.1 or 0.45 w/c, and the remaining water wasthen added and mixing completed. Carbon uptake at various time pointswas measured, as shown in FIG. 44. The rate of carbon dioxide uptake washigher for the paste with w/c 0.1 at time of reaction than for w/c of0.45.

In a second study, a series of tests were performed on mortar. Mortarmix made under a 20 LPM flow of CO₂ gas. The carbon dioxide content wasmeasured and a curve constructed relating the w/c of the mortar mix atthe time of carbon dioxide addition to the approximate amount of CO₂uptake. Mix design was 1350 g EN sand, 535 g of cement (Holcim GU),267.5 g of water. Total w/c=0.5 Water was added in two stages. Oneportion before carbonation, the remaining portion after 1 min ofcarbonation. The amount before carbonation ranged from 10% to 100% oftotal (w/c=0.05 to 0.50). The effect of w/c on carbonation at 1 minuteis shown in FIG. 45 and TABLE 16.

TABLE 16 Effect of w/c in mortar on carbon dioxide uptake Relative toinitial w/c Uptake 0.05 level 0.50 0.00 0.05 1.98 100% 0.10 1.56 79%0.15 1.52 77% 0.20 1.29 65% 0.25 1.32 67% 0.30 1.24 63% 0.35 0.77 39%0.40 0.78 40% 0.45 0.48 24% 0.50 0.35 18%

Drier mortar systems showed higher rates of uptake than did wet systems.1.98% uptake at 0.05 w/c declined to 0.35% at 0.50 w/c.

In a third test, a trial concrete mix was prepared with split wateradditions. The total mix was 300 kg/m³ cement, 60 fly ash, 160 water,1030 stone, 832 sand. The water was added in two stages. CO₂ suppliedfor 180 seconds at 80 LPM after the first water addition. Remainingwater then added and mixing completed. The w/c at carbon dioxideaddition was 0.1, 0.15, or 0.45. The results are shown in FIG. 46. Aswith mortars, the carbon uptake increased with lower w/c when the carbondioxide is delivered.

Example 19

This Example illustrates that temperature rise during carbonation of ahydraulic cement mix is highly correlated with degree of carbonation andcan be used as an indicator of degree of carbonation in a specificsystem.

In a first test, the mortar used in the second test of EXAMPLE 17 alsohad temperature measurements taken at the various time points. Theresults are shown in FIG. 47. There was a linear relationship betweendegree of carbonation and temperature increase in this system, in whichw/c was varied and carbon dioxide exposure was kept constant.

In a second test, temperature vs. carbon dioxide uptake was studied inmortars prepared with three different cements, Holcim GU, LafargeQuebec, and Lehigh. Mortar was prepared at a w/c=0.5 and carbonated forvarious times at 20 LPM CO2. The results are shown in FIG. 48. There wasalso a linear relationship between degree of carbonation and temperaturerise in this system, in which w/c was kept constant at 0.5 and time ofcarbon dioxide exposure was varied. The relationship was relativelyconstant over different cement types. The slopes of the line differ inthe two tests, which were conducted in two different systems, reflectingthe specificity of temperature rise with carbonation to a particularsystem.

These results indicate that in a well-characterized system, temperatureincrease may be used as a proxy indicator for carbon dioxide uptake.

Example 20

This Example illustrates the effects of different admixtures on slumpand compressive strength in concrete.

In a first test, sodium gluconate at 0, 0.1% or 0.2% was added to aconcrete mix after carbonation and the effects slump at 1, 10 and 20minutes after mixing were measured, and compared to control,uncarbonated concrete. The results are shown in FIG. 49 and TABLE 17.The slump of the carbonated concrete is less than half of the control at1 min and declines to no slump at 10 min. Adding 0.1% sodium gluconateafter carbonation gave a slump equal to the control at 1 min, 80% at 10min and 50% at 20 min. Adding 0.2% also provided high slump than thelower dose at all intervals, before being 75% of the control at 20 min.

TABLE 17 Effects of sodium gluconate on concrete slump Control CO₂Control SG - 0.1% SG - 0.2%  1 min 100% 46% 100% 108% 10 min 100% 0% 80%140% 20 min 100% 0% 50% 75%

In a second test, the effects of fructose at various concentrations oninitial slump of a concrete mix were tested. Fructose was added aftercarbonation. Total mix was 4.22 kg cement, 1 kg fly ash, 3.11 kg water,16.96 kg stone, 14.21 kg sand. The results are shown in FIG. 50.Carbonation reduced the slump of the concrete. In response, fructose wasadded after carbonation is proportions of 0.05, 0.10 and 0.20% by weightof cement. The dosages reflect solid mass of additive delivered in asolution. The CO₂ content was quantified as 1.3%, 1.4% and 1.5% byweight of cement for the three carbonated batches respectively. 0.20%fructose was sufficient to restore the slump to be equivalent to thecontrol. However, fructose had a strength retarding effect, as shown inFIG. 51. Strength at 24 hours was significantly less than uncarbonatedcontrol, but strengths at 7 days was acceptable, with higher strengthsassociated with higher fructose contents.

Example 21

In this Example, a variety of different cements were tested in a mortarmix to determine variations in response to carbonation.

Six cements were tested: Holcim GU (Hol), Lafarge Quebec (LQc), LafargeBrookfield (LBr), Lehigh (Leh), Illinois Product (Ipr), and NorthfieldFed White (NWh). The properties and chemistries of the different cementsare given in TABLE 18.

TABLE 18 Properties and chemistries of different cements Metric Hol LQcLBr Leh IPr NWh Surface Area- 423 417 392 425 501 408 Blaine (m²/kg)Free CaO (%) 0.31 0.94 0.16 1.45 1.45 1.47 CaO (%) 62.22 60.56 62.6861.55 62.61 65.36 Na₂O_(e) (%) 0.28 0.38 0.18 0.11 0.41 0.08 SiO₂ (%)20.30 19.18 20.10 19.53 19.12 21.41 Al₂O₃ (%) 4.62 4.72 5.24 4.45 5.474.38 TiO₂ (%) 0.22 0.21 0.26 0.32 0.29 0.08 P₂O₅ (%) 0.14 0.26 0.05 0.250.13 0.01 Fe₂O₃ (%) 2.50 2.74 2.27 3.00 2.23 0.20 MgO (%) 2.21 2.80 1.483.21 2.70 0.90 Na₂O (%) 0.22 0.32 0.11 0.06 0.34 0.06 K₂O (%) 0.92 0.841.09 0.70 1.01 0.28 Mn₂O₃ (%) 0.05 0.09 0.07 0.18 0.19 0.01 SrO (%) 0.080.24 0.06 0.04 0.07 0.03 SO₃ (%) 3.63 3.79 4.10 2.96 3.88 3.94 BaO (%)0.06 0.05 0.13 0.05 0.05 0.08 ZnO (%) 0.04 0.07 0.00 0.02 0.01 0.00Cr₂O₃ (%) 0.01 0.03 0.01 0.01 0.01 0.00 Loss on ignition 2.52 4.08 2.383.54 1.98 3.00 to 975° C. (%)

The mortar mix was EN 196 Sand 1350 g, Cement 535 g, Water 267.5 g, w/cRatio 0.5. CO₂ was added to the mixing bowl at 20 LPM for durations of0, 2, 4, 6, and 8 minutes. Temperature change, slump, flow-spread, CO₂uptake, and 24 hr cube strength were measured. The results are given inTABLE 19.

TABLE 19 Properties of carbonated mortars made with different cementsHol LQc LBr Leh IPr NWh 0 CO₂ Uptake 0.00 0.00 0.00 0.00 0.00 0.00 min(% bwc) CO₂ Delta T (° C.) 0.0 1.1 1.2 0.7 1.3 1.0 Slump (mm) 110 115100 110 95 105 Slump (% of 100% 100% 100% 100% 100% 100% Control) Work(mm) 157 185 144 165 130 180 Strength (MPa) 20.2 15.0 25.1 16.0 33.420.4 Strength (% of 100% 100% 100% 100% 100% 100% Control) 2 CO₂ Uptake(% bwc) 0.87 0.64 0.47 0.67 0.55 0.69 min Delta T (° C.) 2.9 3.6 2.8 4.33.7 6.5 CO₂ Slump (mm) 70 105 40 50 10 30 Slump (% of Control)  64%  91% 40%  45%  11%  29% Work (mm) 83 140 58 60 10 35 Strength (MPa) 9.9 7.612.0 13.1 31.3 17.3 Strength (% of  49%  38%  48%  65%  94%  85%Control) 4 min CO₂ Uptake 0.94 0.88 1.10 1.30 1.79 0.88 CO₂ (% bwc)Delta T 4.9 6.1 7.6 7.2 9.3 9.3 (° C.) Slump 60 70 20 45 0 8 (mm) Slump(%  55%  61%  20%  41%  0%  8% of Control) Work (mm) 75 78 21 45 0 10Strength 9.9 8.1 11.2 10.9 27.5 16.4 (MPa) Strength (%  49%  40%  45% 54%  82%  80% of Control) 6 CO₂ Uptake (% bwc) 1.96 1.74 4.06 1.84 2.711.57 min Delta T (° C.) 7.6 9.2 9.7 11.2 13.2 12.7 CO₂ Slump (mm) 35 700 35 0 0 Slump (% of Control)  32%  61%  0%  32%  0%  0% Work (mm) 35 89−6 37 0 0 Strength (MPa) 8.8 6.4 11.2 13.4 29.5 — Strength (% of  43% 32%  45%  66%  88% — Control) 8 min CO₂ Uptake (% bwc) 2.76 1.68 1.272.23 3.75 2.07 CO₂ Delta T (° C.) 13.4 9.2 14.8 14.7 22.2 17.3 Slump(mm) 5 40 0 15 0 0 Slump (% of Control)  5%  35%  0%  14%  0%  0% Work(mm) 5 44 −8 13 0 0 Strength (MPa) 8.2 6.8 13.9 14.5 — — Strength (% ofControl)  41%  34%  56%  72% — —

There was considerable variation among the mortars made from thedifferent cements in slump and strength. The Illinois Product wasnotable for its higher compressive strength at all time points tested.Without being bound by theory, this may be due to its greater surfacearea (see TABLE 18), which allows it to absorb carbon dioxide withrelatively less proportional impact on strength development. Strengthvs. surface area of carbonated mortar mixes with various surface areasis shown in FIG. 52.

Example 22

In this Example, various admixtures were added to cement paste mixesexposed to carbon dioxide and their effects on slump after mixing weredetermined. The paste mix was 500 g cement, 250 g water. Holcim GUcement. 1% bwc CO2 was dosed, with mixing for one minute. The resultsare shown in TABLE 20.

TABLE 20 Effects of admixtures on slump of carbonated mortar ConditionPaste Spread (cm) (all doses expressed as 1 Min Paste Spread (cm) % byweight of cement) after mixing 10 Min after mixing Control 11.5 13.75 1%CO₂ 8.75 5 1% CO₂ + 1% Na₂SO₄ 9.75 4.25 1% CO₂ + 3% Na₂SO₄ 7.25 4 1%CO₂ + 5% Na₂SO₄ 4.75 4 1% CO₂ + 0.04% Citric Acid 6.75 4 1% CO₂ + 0.10%Gluconate 6.5 4.25 1% CO₂ + 0.15% Gluconate 9.25 9.75 1% CO₂ + 0.20%Gluconate 9.25 10.25 1% CO₂ + 0.05% Gluconate - 9.75 4.75 AfterCarbonation 1% CO₂ + 0.10% Gluconate - 10.75 11.775 After Carbonation 1%CO₂ + 0.15% Gluconate - 13.5 14 After Carbonation

Example 23

In this Example, sensors for carbon dioxide and moisture were used in amixing operation.

A precast operation was performed using the following mix components:

Aggregate Fine Shaw Resources 602 kg Sand Aggregate Coarse ⅜″ Coldstream200 kg Aggregate Coarse Granodiorite 839 kg Cement Cement Maxcem 286 kgAdmix Rheopel Plus 400 ml Admis Rheofit 900 350 ml

Two carbon dioxide sensors were used, Sensor 1 positioned adjacent to anaccess hatch to the mixer and Sensor 2 positioned at the ejectionlocation of the mixer, at a door that discharges onto a belt. CO₂ dosewas increased or decreased depending on the overspill, as detected bythe two sensors.

They are involved in a two stage injection approach.

1. Fill—high flowrate to fill the mixer with CO₂

2. Supply—lower flowrate to maintain a supply as CO₂ is absorbed by theconcrete.

The PLC was programmed as follows to make changes based on the readingsof the CO₂ sensors:

Sensor 1 to be placed by door, sensor 2 placed by mixer exit (measureeach sensor separately)

If sensor 1 exceeds X ppm during flow 1, go to flow 2

If sensor 1 exceeds X ppm during flow 2, reduce flow by reducepercentage

If sensor 2 exceeds Y ppm ever, reduce max mix time by reduce time

If either sensor exceeds 5000 ppm for more than 5 mins, pop-up alarm onscreen

If either sensor exceeds 5000 ppm for more than 10 mins, shut off system

If either sensor exceeds 9000 ppm, shut system off

X and Y were programmable under each recipe (this allows change if aplant has a high CO₂ baseline due to dust etc.). Flow 1 was programmableand was the flow that was used to fill the headspace quickly (usually˜1500 LPM). Flow 2 was calculated by the PLC and was based on max mixtime, CO₂ dose and the total already in the headspace. Max mix time wasprogrammable and was the total desired injection time. Reduce percentageand reduce time were programmable and were determine by what percentageto reduce either the flowrate (thus reducing total CO2 dosage) or themax mix time (thus increasing flowrate to inject in shorter time).

The system was used over several batches and the results are shown inFIG. 53. The top line of FIG. 53 indicates the actual CO₂ dosed, and thesecond line indicates CO₂ detected in the mix. The efficiency of uptakevaried from 60 to 95%. The bottom two lines indicate maximum valuesdetected at Sensor 1 (all batches including Batch 3) and Sensor 2(Batches 4-10). Average values may produce a better result.

This Example demonstrates that carbon dioxide sensors may be used toadjust the flow of carbon dioxide in a cement mixing operation,producing uptake efficiencies up to 95%.

Example 24

This example demonstrates the use of solid carbon dioxide (dry ice) as adelivery mode for carbon dioxide in mixing concrete.

A solid particle of carbon dioxide will sublimate when in contact withthe mix water, thereby releasing carbon dioxide gas over the period oftime required to consume the particle. To achieve an extended dosing ofcarbon dioxide, e.g., in a readymix truck, solid carbon dioxide can beadded in the desired masss and quantity, and in appropriate shape andsize, to effectively provide a given dose of carbon dioxide over adesired length of time. The shape and size of the solid carbon dioxidewill determine the total surface area of the solid; the greater thesurface area, the greater the rate of sublimation of the dry ice.

Two dosing procedures were used. In the first, dry ice in the form ofone inch pellets was used. In the second, a square slab with a 2″ by 2″cross section was cut to the appropriate length to provide the desireddose. Mixing was performed in either a small drum mixer (17 liters) orlarge drum mixer (64 liters), and the mixing was conducted with a coverunless otherwise indicated.

Pellet Delivery:

A mix design of 400 kg/m³ cement, 175 kg/m³ water, 1040 kg/m³ stone, and680 kg/m³ sand was used. Cement in one batch was 26.14 kg.

In a first batch, CO₂ at 0.5% bwc dose of pellets (34 g) was added withthe other mix materials and the concrete was mixed for 2 minutes. Uptakewas found to be 014% bwc, and a 1° C. temperature increase was noted.The dry ice pellets had not completely sublimed after 2 min of mixing.

In a second batch, CO₂ at 1.0% bwc dose of pellets (68 g) was added withthe other mix materials and the concrete was mixed for 4 minutes. CO₂uptake was 0.3% bwc with a 1° C. temperature increase. After 4 min ofmixing, all the dry ice pellets had completely sublimed.

In a third batch, CO₂ at 2.75% bwc dose of pellets (186 g) was addedwith the other mix materials and the concrete was mixed for 4 minutes.CO₂ uptake was 0.6% bwc with a 2° C. temperature rise; all dry icepellets were sublimed after 4 min of mixing.

With the use of pellets, uptake increased with increasing pellet dose,and pellets of this size and in these doses took 2 to 4 min tocompletely sublime. CO₂ uptake was low efficiency, and the gas uptakewas associated with mix stiffening.

Slab Delivery:

In a first test, the same mix design as for the pellet tests was used.The 2×2″ slab was cut to 5.5″ long for a dose of 2% CO₂ bwc. In a firstbatch, water was added in two additions. A first addition of water tow/c of 0.2 was performed, the the dry ice slab was added and mixed for40 seconds. Final water was added to the total water amount and theconcrete was mixed for an additional 6 min. The CO₂ uptake was 0.95% andno temperature increase was observed. In a second batch, 4 serialaddition of slabs of dry ice were performed. All water was added to themix (w/c 0.44) then a dry ice slab was added for a dose of 2% bwc. Theconcrete was mixed for 6 min. CO₂ uptake was 0.67% and no temperatureincrease was observed. An additional slab of dry ice was added to themix, at 2% bwc for a total dose of 4% bwc, and a further 6 minutes ofmixing was performed. CO₂ uptake was 1.67%, and no temperature increasewas observed. An additional slab of dry ice was added to the mix, at 2%bwc for a total dose of 6% bwc, and a further 6 minutes of mixing wasperformed. CO₂ uptake was 2.33%, and a 3.5° C. temperature increase wasobserved. An additional slab of dry ice was added to the mix, at 6% bwcfor a total dose of 12% bwc, and a further 6 minutes of mixing wasperformed. CO₂ uptake was 3.44%, and a 5° C. temperature increase wasobserved. In this test, in which mixing was at full speed, all thecarbon dioxide was completely sublimed at the end of each mixing time.Subsequent tests were performed at lower speed representative of a truckin transit rather than a truck in initial mixing stage.

In a second test, the same mix design as for the pellets was used exceptthe final proportion of water was 200 kg/m³. Slow mixing (˜1 RPM) in a65 L mixer was performed, with a dry ice slab added 2 min after theinitial cement and water contact, for a dose of 2% bwc. Mixing wascontinued for a total of 36 min. CO₂ uptake was 0.95%, and a 3.5° C.temperature increase was observed. The slump of the concrete mix priorto CO₂ addition was 6″, and 3″ after 36 min of mixing under CO₂.

In a third test, the same mix design as for the pellet tests was used.Water was added to an initial w/c of 0.2, a dry ice slab was added for adose of 0.2% bwc, and the concrete mix was mixed for 40 s at full speed(45 rpm), then the remainder of the water was added, to a w/c of 0.45and the mix was mixed for 36 min of slow (transit, ˜1 RPM) mixing of thebatch in a 65 L mixer. CO₂ uptake was 0.75%, and a 1.5° C. temperatureincrease was observed. Slump was 5.5″ after 36 min of mixing. A controlslump (without carbon dioxide) was assumed to be ˜6″. Then another 2%bwc of dry ice slab was added, and the concrete was mixed at high speedfor an additional 11 min. CO₂ uptake was 1.66%. Slump decreased from5.5″ to 2.5.″

In a fourth test, the same mix design as for the pellet tests was used,except water was 195 kg/m³. Two batches were run in which dry ice at adose of 2% bwc was added 2 minutes after the initial cement and watercontact. In the first batch, the concrete was mixed with cover on at afast transit mix (˜2 RPM) for 30 min. CO₂ uptake was 1.3% bwc, and a 5°C. temperature increase was observed. Slump was 0″ after mixing,compared to 6.5″ slump in control (no carbon dioxide). In the secondbatch, mixing was done with cover off at a fast transit mix for 29 min.CO₂ uptake was 0.7% bwc, and a 0.2° C. temperature increase wasobserved. Slump was 3″ after 29 min mixing, compared to 6.5″ slump incontrol (no carbon dioxide).

This Example demonstrates that the size and shape of dry ice can be usedto control delivery, and that various times of addition, mix rates,water contents, and other variables may be manipulated to modulate theamount of carbon dioxide taken up by the concrete and the effect of thecarbon dioxide on such factors as slump.

Example 25

This Example illustrates the use of low-dose carbon dioxide to provideaccelerated hydration, early strength development and set, with minimalimpact on rheology and later-age strength.

Mortar Tests

In a first set of tests, mortars were prepared. Mortars were preparedwith 1350 g sand, 535 g cement, and 267.5 g water, and homogenized in apaddle-style mixer by mixing on low speed for ˜2 min, then samples wereremoved for CO₂ analysis and calorimetry. The mortar was then exposed toCO₂ gas at a flow rate of ˜0.15 LPM for 2 minutes and additional sampleswere removed. This same mortar was exposed to 3-7 successive rounds ofcarbonation total, with samples removed between each round.

In one test, Holcim GU cement was used. The levels of carbonation of themortar achieved in succeeding rounds of carbon dioxide exposure were 0,0.05, 0.10, 0.20, 0.48, and 0.70% bwc. FIG. 54 presents data onisothermal calorimetry power curves for the different levels ofcarbonation, showing that by carbonating the mortar the rate of cementhydration could be accelerated (curves shift to the left and becomesteeper with carbonation). The total heat evolution was also improved atearly ages with carbonation of the mortars (FIG. 55).

In addition, the onset of both initial and final set was accelerated bycarbonation, as indicated by penetrometer measurements and shown in FIG.56. For these measurements, mortar was prepared as follows: 5× batchsize in Hobart (normal batch scaled up 500% to use in a larger mixer)1337.5 g water, 2675 g cement 5175 g sand. Combined in Hobart mixer andhomogenized. Carbonated at 1.0 LPM for 5 rounds of 2 minutes (i.e. 0, 2,4, 6, 8, 10 minutes samples). Penetrometer measurement performed on lastsample (10 minutes total CO₂ exposure). Expected dose for 1 LPM for 10min is about 20 g of CO₂, for a total dose is about 0.74% bwc. FromEltra: carbon dioxide uptake estimated at 0.10% bwc. The low uptake mayhave been due to head space/flow rate. A Control was then cast forcomparison afterwards. 2× batch size in Kitchen Aid (smaller mixer):1070 g cement, 535 g water, 2070 g sand.

Similar results were seen for mortars prepared with Lafarge BrookfieldGU cement dosed at 0, 0.07 0.14, and 0.22% bwc carbon dioxide, as shownfor hydration in FIG. 57, as well as early strength development as shownin FIG. 58.

Concrete Tests

Tests were extended to concretes. In a typical experiment a batch ofconcrete was prepared with the following proportions: 16.0 kg sand,23.80 kg stone, 9.18 kg cement, 3.15 kg water. The concrete washomogenized in a drum-style mixer by mixing on low speed for ˜2 min andsamples were removed for CO₂ analysis and calorimetry. The concrete wasthen exposed to CO₂ gas at a flow rate of ˜2.0 LPM for 2 minutes andadditional samples were removed. This same concrete was exposed to threesuccessive rounds of carbonation in total, with samples removed betweeneach round. Total CO₂ uptake for succeeding rounds was 0, 0.10, 0.15,and 0.20% bwc.

In a first series, LaFarge Brookfield GU cement was used in theconcrete. Calorimetry power curves show acceleration of concrete. SeeFIG. 59. Calorimetry energy curves show an increased amount of heatreleased at all ages in the carbonated concrete. See FIG. 60. Earlystrength development was also accelerated in the carbonated concretes.See FIG. 61. In addition, set time measurements confirmed that theobserved acceleration of hydration translated into accelerated initial(500 psi) and final (4000 psi) set in the carbonated concrete. FIG. 62shows penetrometer readings over time for carbonated concrete(approximately 0.20% bwc CO₂ uptake) compared to uncarbonated.

Similar results were obtained in a second series, where concrete wasproduced with St. Mary's B cement; for example, carbonation at 0.08,0.17, and 0.35% bwc all produced increased 8-hour and 12-hourcompressive strength compared to uncarbonated control. See FIG. 63.

Other concretes were produced using St. Mary's HE cement and Holcim GUcement (carbonated at a single level of CO₂ uptake). The concretes werecarbonated at a constant carbon dioxide exposure of delivered carbondioxide at a rate of 0.10-0.15% bwc per minute over three minutes (2 minwith carbon dioxide flow and one minute of lid on mixing after delivery)for a total dose of 0.20-0.30% carbon dioxide bwc. Carbonation level was0.15% bwc in the Holcim GU mixture and 0.26% bwc in the St Mary's HEmixture. See TABLE 21

TABLE 21 Properties of low dose carbonated concretes Initial Set FinalSet Strength Acceleration Acceleration Strength at 8 hr at 8 hr CementID (minutes) (minutes) (% of control) (MPa) St. Mary's HE 55 41 133 2.2Holcim GU 61 70 149 1.3

In an industrial trial, a truck carrying 2 m3 of concrete was deliveredto the lab, with a mix design of 1930 kg sand, 2240 kg stone, 630 kgLaFarge Brookfield GU cement, and 238 kg water. A sample of uncarbonatedconcrete was first removed from the truck to cast control samples. Thetruck was then subjected to 6 separate doses of 0.05% bwc CO₂. Enoughconcrete was removed to satisfy casting demands following each dose (˜60L). The fresh properties of the concrete are shown in TABLE 22.

TABLE 22 Fresh properties of readymix concrete at low dose carbonationMighty Temp at Air Defoamer 21ES Sample Sample Total CO₂ Time ofdischarge Slump Content Dose dose # ID dose (bwc) discharge (° C.)(inches) (%) (% bwc) (% bwc) 1 Control 0 8:45 14.7 3.5 1.5 0.10 0.10 2CO₂-1 0.05 8:50 16.4 3.5 n/a 0.10 0.10 3 CO₂-2 0.10 9:04 16.7 3.5 n/a0.10 0.10 4 CO₂-3 0.15 9:12 18.0 3.0 n/a 0.10 0.10 5 CO₂-4 0.20 9:2618.4 3.0 n/a 0.10 0.10 6 CO₂-5 0.25 9:35 18.5 1.5 n/a 0.10 0.10 7 CO₂-60.30 9:50 18.7 2.0 n/a 0.10 0.15

In general, the compressive strength of the concrete specimens increasedwith each additional round of carbonation. This was most evident atearly ages (up to 74% increase at 12 hours) but persisted until laterages (5% compressive strength incrase at 7 days). See FIGS. 64 (12hours), 65 (16 hours), 66 (24 hours), and 67 (7 days).

This Example illustrates that the use of low-dose carbon dioxide inmortar and concrete mixes can accelerate set and strength developmentcompared to uncarbonated mortar and concrete mixes.

Example 26

This Example demonstrates the use of sodium gluconate in a dry mixconcrete, either carbonated or uncarbonated.

The mix was 200 g stone, 1330 g sand, 330 g Holcim GU cement, and 130 gwater. The mixing cycle was:

-   -   Mix aggregates and water for 30 s    -   Add cement and mix 30 s    -   60 s mixing, with carbonation if called for    -   add admixtures and mix 30 s    -   Compact cylinders using Proctor hammer    -   Dosages employed were 0, 0.02%, 0.04% and 0.06% sodium gluconate        by mass of cement.

FIG. 68 shows the CO₂ uptake of carbonated specimens. The masses of thecylinders prepared, a proxy for density since all cylinder volumes aresubstantially the same, showed that carbonation resulted in an 8.4% massdeficit in comparison to the control, but that the addition of sodiumgluconate increased the mass of the carbonated specimens, proportionalto the dose, so that at a dose of 0.06% sodium gluonate, the massdeficit was reduced to 5.5%, whereas none of the three sodium gluconatedoses had an effect on the compaction of the control samples. See FIGS.69 and 70. Retardation was quantified through calorimetry by determiningthe amount of energy released through the first 6 hours following themix start. Carbonation caused a decrease in energy released, as did theaddition of sodium gluconate; in carbonated specimens the reduction inenergy released was 19% at the highest sodium gluconate dose, whereas inuncarbonated specimens the reduction in energy released was 53% at thehighest sodium gluconate dose. See FIGS. 71 and 72.

Example 27

This Example demonstrates the effects of increasing free lime on carbondioxide uptake and hydration.

In a first test, mortars were prepared with added CaO (1.5% bwc), NaOH(2.2% bwc), or CaCl₂ (3% bwc), carbonated, and compared to control. Astandard mortar mix of 535 g cement, 2350 g sand, and 267.5 g water wasused. The sand and water were combined and mixed for 30 s, followed bycement addition (with added powder if used) and an additional 60 smixing. Initial temperature was recorded, then the mortar was mixed for60 s under 20 LPM CO₂ flow, mixing was stopped and temperature recordedand sample removed for CO₂ analysis, then mixing and CO₂ exposure wasresumed for another 60 s and sampling occurred, for a total of 5 min ofCO₂ exposure. The results are shown in FIG. 73. Addition of the alkalispecies, free lime (CaO) or NaOH, increased the rate of CO₂ uptake,while the addition of CaCl₂ decreased the uptake rate. The rates ofuptake were: 0.34% CO₂ uptake/min (no additive); 0.56% CO₂ uptake/min(CaO), a 66% increase; 0.69% CO₂ uptake/min (NaOH), a 104% increase; and0.23% CO₂ uptake/min (CaCl2), a 34% decrease.

In a second test, two test mortars were compared, one conventionalmortar and one that included an addition of 1.5% CaO bwc. The mortarmixes were as in the first test. The cement used had a free lime contentof 0.31% bwc before addition of extra CaO; this is considered to be alow free lime level. The mixing mortar was subjected to 0, 30, 60, or 90s of CO₂ at 20 LPM, and hydration was measured by calorimetry. Energyrelease was followed up to 24 hours at 6 hour intervals.

The results are presented in FIG. 74. When control (no CaO addition)carbonated vs. uncarbonated mortars were compared, energy release with30 s CO₂ was 19% greater in the carbonated compared to uncarbonated at 6hours, declining to 7% lower at 24 hours; energy release with 60 s CO₂was 23% greater in the carbonated compared to uncarbonated at 6 hours,declining to 12% lower at 24 hours; energy release with 90 s CO₂ was 21%greater in the carbonated compared to uncarbonated at 6 hours, decliningto 17% lower at 24 hours. See FIG. 75. In general, addition of CaO tothe mix both increased CO₂ uptake for a given time of exposure, andincreased the energy release at a given time point, compared to sampleswithout CaO addition. When compared to a control mortar that containedno added CaO, mortars with added CaO showed energy release at 97-99% ofcontrol at all time points in uncarbonated samples; in samples exposedto 30 s CO₂, mortars with added CaO showed energy release 20% higherthan mortars with no added CaO at 6 hours, decreasing to 11% higher at24 hours, and CO₂ uptake was 56% greater than in mortars with no addedCaO; in samples exposed to 60 s CO₂, mortars with added CaO showedenergy release 33% higher than mortars with no added CaO at 6 hours,decreasing to 15% higher at 24 hours, and uptake was 151% greater thanin mortars with no added CaO; in samples exposed to 90 s CO₂, mortarswith added CaO showed energy release 23% higher than mortars with noadded CaO at 6 hours, decreasing to 9% higher at 24 hours, and uptakewas 151% greater than in mortars with no added CaO. See FIG. 76.

This Example demonstrates that free lime (CaO) addition to a mortar bothimproves the rate of carbon dioxide uptake as well as hydration, whencompared to mortar without added free lime.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention.

What is claimed is:
 1. A system for carbonating a cement mix at a mixsite comprising (i) a mixer for mixing the cement mix; (ii) an apparatusto deliver carbon dioxide to the cement mix while the mix is mixing;(iii) a telemetry system to transmit information regarding the cementmix to a central location remote from the mix site, wherein the centrallocation stores data regarding the cement mix for use in future cementmixes and/or for use in modification of the same or similar cement mixin the mixer or in other mixers.
 2. The system of claim 1 wherein themixer is a stationary mixer.
 3. The system of claim 1 wherein the mixeris a transportable mixer.
 4. The system of claim 3 wherein thetransportable mixer comprises a drum of a ready mix truck.
 5. The systemof claim 1 comprising a plurality of mix sites at a plurality oflocations, each of which comprises a mixer for mixing a cement mix, anapparatus for carbonating the cement mix while it is mixing, and atelemetry system for transmitting information regarding the cement mixto a central location wherein the central location stores data regardingthe cement mix for use in future cement mixes and/or for use inmodification of a future cement mix of the same or similar cement mix inthe mixer or in other mixers.
 6. The system of claim 5 wherein theplurality of mixers comprises at least 3 different mixers at 3 differentlocations.
 7. The system of claim 1 wherein the information regardingthe cement mix comprises information regarding carbon dioxide uptake ofthe cement mix, rheology of the cement mix at one or more time points,strength of the cement mix at one or more time points, shrinkage of thecement mix, water absorption of the cement mix, elastic modulus of thecement mix, density of the cement mix, permeability of the cement mix,calcite content of the cement mix, or a combination thereof.
 8. Thesystem of claim 7 wherein the information comprises informationregarding rheology of the cement mix at one or more time points,strength of the cement mix at one or more time points, or a combinationthereof.
 9. The system of claim 1 wherein the modification of a futurecement mix comprises modification of (a) total amount of carbon dioxideadded to the cement mix, (b) rate of addition of carbon dioxide, (c)time of addition of carbon dioxide to the cement mix, (d) whether or notan admixture is added to the cement mix, (e) type of admixture added tothe cement mix, (f) timing of addition of admixture to the cement mix,(g) amount of admixture added to the cement mix, (h) amount of wateradded to the cement mix, (i) timing of addition of water to the cementmix, (j) cooling the cement mix during or after carbon dioxide addition,or a combination thereof.
 10. The system of claim 9 wherein themodification of a future cement mix comprises modification of totalamount of carbon dioxide added to the cement mix.
 11. The system ofclaim 2 wherein the stationary mixer is a batch mixer in a ready-mixoperation.
 12. The system of claim 5 wherein each of the mix sitescomprises one or more sensors and/or one or more controllers that sendinformation to the telemetry system for the mix site to be sent to acontroller at the central location.
 13. The system of claim 12 whereinthe controller at the central location is configured to process theinformation transmitted by the sensors and/or controllers and provideupdated and/or modified mix instruction to the cement mix operations.14. The system of claim 5 wherein the controller at the central locationis configured to learn from the transmitted information and to provideupdated and/or modified information to the mix operations based on saidlearning.
 15. The system of claim 6 wherein the plurality of mixerscomprises at least 10 separate mixers.
 16. The system of claim 1 furthercomprising a human machine interface (HMI) for inputing informationmanually to be sent via the telemetry system to the central location.17. The system of claim 1 wherein the apparatus to deliver carbondioxide to the mixer is configured to convert liquid carbon dioxide tosolid and gaseous carbon dioxide and deliver the mixture to the cementmix.
 18. The system of claim 17 wherein the apparatus is configured todeliver a mixture of solid and gaseous carbon dioxide to the mixer in aratio of 1:2 to 2:1 solid:gaseous carbon dioxide.
 19. The system ofclaim 17 configured to deliver the carbon dioxide to the cement mix in adose of 0.01-15% by weight cement (bwc).
 20. The system of claim 1wherein the apparatus to deliver carbon dioxide to the cement mix isconfigured to deliver carbon dioxide to the surface of the cement mixfrom an opening or plurality of openings that are at least 100 cm fromthe surface of the cement mix.